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2877 lines
68 KiB
2877 lines
68 KiB
/* |
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
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* |
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* This file is released under the GPL. |
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*/ |
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|
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#include <linux/blkdev.h> |
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#include <linux/device-mapper.h> |
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#include <linux/delay.h> |
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#include <linux/fs.h> |
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#include <linux/init.h> |
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#include <linux/kdev_t.h> |
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#include <linux/list.h> |
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#include <linux/list_bl.h> |
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#include <linux/mempool.h> |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/vmalloc.h> |
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#include <linux/log2.h> |
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#include <linux/dm-kcopyd.h> |
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|
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#include "dm.h" |
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|
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#include "dm-exception-store.h" |
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|
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#define DM_MSG_PREFIX "snapshots" |
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static const char dm_snapshot_merge_target_name[] = "snapshot-merge"; |
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|
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#define dm_target_is_snapshot_merge(ti) \ |
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((ti)->type->name == dm_snapshot_merge_target_name) |
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|
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/* |
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* The size of the mempool used to track chunks in use. |
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*/ |
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#define MIN_IOS 256 |
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#define DM_TRACKED_CHUNK_HASH_SIZE 16 |
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#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ |
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(DM_TRACKED_CHUNK_HASH_SIZE - 1)) |
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|
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struct dm_exception_table { |
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uint32_t hash_mask; |
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unsigned hash_shift; |
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struct hlist_bl_head *table; |
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}; |
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|
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struct dm_snapshot { |
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struct rw_semaphore lock; |
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|
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struct dm_dev *origin; |
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struct dm_dev *cow; |
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struct dm_target *ti; |
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|
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/* List of snapshots per Origin */ |
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struct list_head list; |
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/* |
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* You can't use a snapshot if this is 0 (e.g. if full). |
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* A snapshot-merge target never clears this. |
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*/ |
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int valid; |
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|
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/* |
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* The snapshot overflowed because of a write to the snapshot device. |
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* We don't have to invalidate the snapshot in this case, but we need |
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* to prevent further writes. |
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*/ |
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int snapshot_overflowed; |
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|
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/* Origin writes don't trigger exceptions until this is set */ |
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int active; |
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|
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atomic_t pending_exceptions_count; |
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spinlock_t pe_allocation_lock; |
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/* Protected by "pe_allocation_lock" */ |
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sector_t exception_start_sequence; |
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|
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/* Protected by kcopyd single-threaded callback */ |
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sector_t exception_complete_sequence; |
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/* |
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* A list of pending exceptions that completed out of order. |
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* Protected by kcopyd single-threaded callback. |
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*/ |
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struct rb_root out_of_order_tree; |
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|
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mempool_t pending_pool; |
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|
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struct dm_exception_table pending; |
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struct dm_exception_table complete; |
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|
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/* |
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* pe_lock protects all pending_exception operations and access |
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* as well as the snapshot_bios list. |
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*/ |
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spinlock_t pe_lock; |
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|
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/* Chunks with outstanding reads */ |
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spinlock_t tracked_chunk_lock; |
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struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; |
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|
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/* The on disk metadata handler */ |
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struct dm_exception_store *store; |
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|
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unsigned in_progress; |
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struct wait_queue_head in_progress_wait; |
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struct dm_kcopyd_client *kcopyd_client; |
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|
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/* Wait for events based on state_bits */ |
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unsigned long state_bits; |
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|
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/* Range of chunks currently being merged. */ |
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chunk_t first_merging_chunk; |
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int num_merging_chunks; |
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|
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/* |
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* The merge operation failed if this flag is set. |
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* Failure modes are handled as follows: |
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* - I/O error reading the header |
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* => don't load the target; abort. |
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* - Header does not have "valid" flag set |
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* => use the origin; forget about the snapshot. |
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* - I/O error when reading exceptions |
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* => don't load the target; abort. |
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* (We can't use the intermediate origin state.) |
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* - I/O error while merging |
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* => stop merging; set merge_failed; process I/O normally. |
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*/ |
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bool merge_failed:1; |
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|
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bool discard_zeroes_cow:1; |
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bool discard_passdown_origin:1; |
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/* |
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* Incoming bios that overlap with chunks being merged must wait |
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* for them to be committed. |
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*/ |
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struct bio_list bios_queued_during_merge; |
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|
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/* |
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* Flush data after merge. |
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*/ |
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struct bio flush_bio; |
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}; |
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|
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/* |
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* state_bits: |
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* RUNNING_MERGE - Merge operation is in progress. |
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* SHUTDOWN_MERGE - Set to signal that merge needs to be stopped; |
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* cleared afterwards. |
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*/ |
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#define RUNNING_MERGE 0 |
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#define SHUTDOWN_MERGE 1 |
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|
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/* |
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* Maximum number of chunks being copied on write. |
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* |
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* The value was decided experimentally as a trade-off between memory |
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* consumption, stalling the kernel's workqueues and maintaining a high enough |
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* throughput. |
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*/ |
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#define DEFAULT_COW_THRESHOLD 2048 |
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|
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static unsigned cow_threshold = DEFAULT_COW_THRESHOLD; |
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module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644); |
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MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write"); |
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|
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DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle, |
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"A percentage of time allocated for copy on write"); |
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struct dm_dev *dm_snap_origin(struct dm_snapshot *s) |
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{ |
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return s->origin; |
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} |
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EXPORT_SYMBOL(dm_snap_origin); |
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struct dm_dev *dm_snap_cow(struct dm_snapshot *s) |
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{ |
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return s->cow; |
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} |
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EXPORT_SYMBOL(dm_snap_cow); |
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static sector_t chunk_to_sector(struct dm_exception_store *store, |
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chunk_t chunk) |
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{ |
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return chunk << store->chunk_shift; |
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} |
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|
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static int bdev_equal(struct block_device *lhs, struct block_device *rhs) |
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{ |
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/* |
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* There is only ever one instance of a particular block |
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* device so we can compare pointers safely. |
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*/ |
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return lhs == rhs; |
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} |
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|
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struct dm_snap_pending_exception { |
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struct dm_exception e; |
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|
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/* |
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* Origin buffers waiting for this to complete are held |
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* in a bio list |
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*/ |
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struct bio_list origin_bios; |
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struct bio_list snapshot_bios; |
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|
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/* Pointer back to snapshot context */ |
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struct dm_snapshot *snap; |
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|
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/* |
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* 1 indicates the exception has already been sent to |
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* kcopyd. |
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*/ |
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int started; |
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|
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/* There was copying error. */ |
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int copy_error; |
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|
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/* A sequence number, it is used for in-order completion. */ |
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sector_t exception_sequence; |
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struct rb_node out_of_order_node; |
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|
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/* |
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* For writing a complete chunk, bypassing the copy. |
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*/ |
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struct bio *full_bio; |
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bio_end_io_t *full_bio_end_io; |
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}; |
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|
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/* |
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* Hash table mapping origin volumes to lists of snapshots and |
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* a lock to protect it |
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*/ |
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static struct kmem_cache *exception_cache; |
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static struct kmem_cache *pending_cache; |
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struct dm_snap_tracked_chunk { |
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struct hlist_node node; |
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chunk_t chunk; |
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}; |
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|
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static void init_tracked_chunk(struct bio *bio) |
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{ |
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); |
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INIT_HLIST_NODE(&c->node); |
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} |
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|
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static bool is_bio_tracked(struct bio *bio) |
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{ |
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); |
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return !hlist_unhashed(&c->node); |
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} |
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static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk) |
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{ |
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); |
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c->chunk = chunk; |
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spin_lock_irq(&s->tracked_chunk_lock); |
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hlist_add_head(&c->node, |
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]); |
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spin_unlock_irq(&s->tracked_chunk_lock); |
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} |
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static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio) |
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{ |
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk)); |
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unsigned long flags; |
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|
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spin_lock_irqsave(&s->tracked_chunk_lock, flags); |
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hlist_del(&c->node); |
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spin_unlock_irqrestore(&s->tracked_chunk_lock, flags); |
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} |
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static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk) |
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{ |
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struct dm_snap_tracked_chunk *c; |
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int found = 0; |
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spin_lock_irq(&s->tracked_chunk_lock); |
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hlist_for_each_entry(c, |
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) { |
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if (c->chunk == chunk) { |
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found = 1; |
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break; |
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} |
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} |
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spin_unlock_irq(&s->tracked_chunk_lock); |
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return found; |
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} |
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/* |
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* This conflicting I/O is extremely improbable in the caller, |
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* so msleep(1) is sufficient and there is no need for a wait queue. |
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*/ |
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static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk) |
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{ |
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while (__chunk_is_tracked(s, chunk)) |
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msleep(1); |
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} |
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|
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/* |
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* One of these per registered origin, held in the snapshot_origins hash |
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*/ |
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struct origin { |
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/* The origin device */ |
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struct block_device *bdev; |
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struct list_head hash_list; |
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/* List of snapshots for this origin */ |
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struct list_head snapshots; |
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}; |
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/* |
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* This structure is allocated for each origin target |
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*/ |
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struct dm_origin { |
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struct dm_dev *dev; |
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struct dm_target *ti; |
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unsigned split_boundary; |
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struct list_head hash_list; |
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}; |
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/* |
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* Size of the hash table for origin volumes. If we make this |
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* the size of the minors list then it should be nearly perfect |
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*/ |
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#define ORIGIN_HASH_SIZE 256 |
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#define ORIGIN_MASK 0xFF |
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static struct list_head *_origins; |
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static struct list_head *_dm_origins; |
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static struct rw_semaphore _origins_lock; |
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static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done); |
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static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock); |
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static uint64_t _pending_exceptions_done_count; |
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static int init_origin_hash(void) |
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{ |
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int i; |
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|
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_origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head), |
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GFP_KERNEL); |
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if (!_origins) { |
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DMERR("unable to allocate memory for _origins"); |
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return -ENOMEM; |
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} |
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for (i = 0; i < ORIGIN_HASH_SIZE; i++) |
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INIT_LIST_HEAD(_origins + i); |
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_dm_origins = kmalloc_array(ORIGIN_HASH_SIZE, |
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sizeof(struct list_head), |
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GFP_KERNEL); |
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if (!_dm_origins) { |
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DMERR("unable to allocate memory for _dm_origins"); |
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kfree(_origins); |
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return -ENOMEM; |
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} |
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for (i = 0; i < ORIGIN_HASH_SIZE; i++) |
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INIT_LIST_HEAD(_dm_origins + i); |
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init_rwsem(&_origins_lock); |
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return 0; |
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} |
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static void exit_origin_hash(void) |
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{ |
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kfree(_origins); |
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kfree(_dm_origins); |
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} |
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static unsigned origin_hash(struct block_device *bdev) |
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{ |
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return bdev->bd_dev & ORIGIN_MASK; |
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} |
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|
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static struct origin *__lookup_origin(struct block_device *origin) |
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{ |
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struct list_head *ol; |
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struct origin *o; |
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|
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ol = &_origins[origin_hash(origin)]; |
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list_for_each_entry (o, ol, hash_list) |
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if (bdev_equal(o->bdev, origin)) |
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return o; |
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|
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return NULL; |
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} |
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|
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static void __insert_origin(struct origin *o) |
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{ |
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struct list_head *sl = &_origins[origin_hash(o->bdev)]; |
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list_add_tail(&o->hash_list, sl); |
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} |
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static struct dm_origin *__lookup_dm_origin(struct block_device *origin) |
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{ |
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struct list_head *ol; |
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struct dm_origin *o; |
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|
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ol = &_dm_origins[origin_hash(origin)]; |
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list_for_each_entry (o, ol, hash_list) |
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if (bdev_equal(o->dev->bdev, origin)) |
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return o; |
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|
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return NULL; |
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} |
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|
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static void __insert_dm_origin(struct dm_origin *o) |
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{ |
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struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)]; |
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list_add_tail(&o->hash_list, sl); |
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} |
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|
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static void __remove_dm_origin(struct dm_origin *o) |
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{ |
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list_del(&o->hash_list); |
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} |
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|
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/* |
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* _origins_lock must be held when calling this function. |
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* Returns number of snapshots registered using the supplied cow device, plus: |
|
* snap_src - a snapshot suitable for use as a source of exception handover |
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* snap_dest - a snapshot capable of receiving exception handover. |
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* snap_merge - an existing snapshot-merge target linked to the same origin. |
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* There can be at most one snapshot-merge target. The parameter is optional. |
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* |
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* Possible return values and states of snap_src and snap_dest. |
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* 0: NULL, NULL - first new snapshot |
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* 1: snap_src, NULL - normal snapshot |
|
* 2: snap_src, snap_dest - waiting for handover |
|
* 2: snap_src, NULL - handed over, waiting for old to be deleted |
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* 1: NULL, snap_dest - source got destroyed without handover |
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*/ |
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static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, |
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struct dm_snapshot **snap_src, |
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struct dm_snapshot **snap_dest, |
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struct dm_snapshot **snap_merge) |
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{ |
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struct dm_snapshot *s; |
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struct origin *o; |
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int count = 0; |
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int active; |
|
|
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o = __lookup_origin(snap->origin->bdev); |
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if (!o) |
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goto out; |
|
|
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list_for_each_entry(s, &o->snapshots, list) { |
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if (dm_target_is_snapshot_merge(s->ti) && snap_merge) |
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*snap_merge = s; |
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if (!bdev_equal(s->cow->bdev, snap->cow->bdev)) |
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continue; |
|
|
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down_read(&s->lock); |
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active = s->active; |
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up_read(&s->lock); |
|
|
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if (active) { |
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if (snap_src) |
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*snap_src = s; |
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} else if (snap_dest) |
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*snap_dest = s; |
|
|
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count++; |
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} |
|
|
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out: |
|
return count; |
|
} |
|
|
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/* |
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* On success, returns 1 if this snapshot is a handover destination, |
|
* otherwise returns 0. |
|
*/ |
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static int __validate_exception_handover(struct dm_snapshot *snap) |
|
{ |
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struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
|
struct dm_snapshot *snap_merge = NULL; |
|
|
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/* Does snapshot need exceptions handed over to it? */ |
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if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, |
|
&snap_merge) == 2) || |
|
snap_dest) { |
|
snap->ti->error = "Snapshot cow pairing for exception " |
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"table handover failed"; |
|
return -EINVAL; |
|
} |
|
|
|
/* |
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* If no snap_src was found, snap cannot become a handover |
|
* destination. |
|
*/ |
|
if (!snap_src) |
|
return 0; |
|
|
|
/* |
|
* Non-snapshot-merge handover? |
|
*/ |
|
if (!dm_target_is_snapshot_merge(snap->ti)) |
|
return 1; |
|
|
|
/* |
|
* Do not allow more than one merging snapshot. |
|
*/ |
|
if (snap_merge) { |
|
snap->ti->error = "A snapshot is already merging."; |
|
return -EINVAL; |
|
} |
|
|
|
if (!snap_src->store->type->prepare_merge || |
|
!snap_src->store->type->commit_merge) { |
|
snap->ti->error = "Snapshot exception store does not " |
|
"support snapshot-merge."; |
|
return -EINVAL; |
|
} |
|
|
|
return 1; |
|
} |
|
|
|
static void __insert_snapshot(struct origin *o, struct dm_snapshot *s) |
|
{ |
|
struct dm_snapshot *l; |
|
|
|
/* Sort the list according to chunk size, largest-first smallest-last */ |
|
list_for_each_entry(l, &o->snapshots, list) |
|
if (l->store->chunk_size < s->store->chunk_size) |
|
break; |
|
list_add_tail(&s->list, &l->list); |
|
} |
|
|
|
/* |
|
* Make a note of the snapshot and its origin so we can look it |
|
* up when the origin has a write on it. |
|
* |
|
* Also validate snapshot exception store handovers. |
|
* On success, returns 1 if this registration is a handover destination, |
|
* otherwise returns 0. |
|
*/ |
|
static int register_snapshot(struct dm_snapshot *snap) |
|
{ |
|
struct origin *o, *new_o = NULL; |
|
struct block_device *bdev = snap->origin->bdev; |
|
int r = 0; |
|
|
|
new_o = kmalloc(sizeof(*new_o), GFP_KERNEL); |
|
if (!new_o) |
|
return -ENOMEM; |
|
|
|
down_write(&_origins_lock); |
|
|
|
r = __validate_exception_handover(snap); |
|
if (r < 0) { |
|
kfree(new_o); |
|
goto out; |
|
} |
|
|
|
o = __lookup_origin(bdev); |
|
if (o) |
|
kfree(new_o); |
|
else { |
|
/* New origin */ |
|
o = new_o; |
|
|
|
/* Initialise the struct */ |
|
INIT_LIST_HEAD(&o->snapshots); |
|
o->bdev = bdev; |
|
|
|
__insert_origin(o); |
|
} |
|
|
|
__insert_snapshot(o, snap); |
|
|
|
out: |
|
up_write(&_origins_lock); |
|
|
|
return r; |
|
} |
|
|
|
/* |
|
* Move snapshot to correct place in list according to chunk size. |
|
*/ |
|
static void reregister_snapshot(struct dm_snapshot *s) |
|
{ |
|
struct block_device *bdev = s->origin->bdev; |
|
|
|
down_write(&_origins_lock); |
|
|
|
list_del(&s->list); |
|
__insert_snapshot(__lookup_origin(bdev), s); |
|
|
|
up_write(&_origins_lock); |
|
} |
|
|
|
static void unregister_snapshot(struct dm_snapshot *s) |
|
{ |
|
struct origin *o; |
|
|
|
down_write(&_origins_lock); |
|
o = __lookup_origin(s->origin->bdev); |
|
|
|
list_del(&s->list); |
|
if (o && list_empty(&o->snapshots)) { |
|
list_del(&o->hash_list); |
|
kfree(o); |
|
} |
|
|
|
up_write(&_origins_lock); |
|
} |
|
|
|
/* |
|
* Implementation of the exception hash tables. |
|
* The lowest hash_shift bits of the chunk number are ignored, allowing |
|
* some consecutive chunks to be grouped together. |
|
*/ |
|
static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk); |
|
|
|
/* Lock to protect access to the completed and pending exception hash tables. */ |
|
struct dm_exception_table_lock { |
|
struct hlist_bl_head *complete_slot; |
|
struct hlist_bl_head *pending_slot; |
|
}; |
|
|
|
static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk, |
|
struct dm_exception_table_lock *lock) |
|
{ |
|
struct dm_exception_table *complete = &s->complete; |
|
struct dm_exception_table *pending = &s->pending; |
|
|
|
lock->complete_slot = &complete->table[exception_hash(complete, chunk)]; |
|
lock->pending_slot = &pending->table[exception_hash(pending, chunk)]; |
|
} |
|
|
|
static void dm_exception_table_lock(struct dm_exception_table_lock *lock) |
|
{ |
|
hlist_bl_lock(lock->complete_slot); |
|
hlist_bl_lock(lock->pending_slot); |
|
} |
|
|
|
static void dm_exception_table_unlock(struct dm_exception_table_lock *lock) |
|
{ |
|
hlist_bl_unlock(lock->pending_slot); |
|
hlist_bl_unlock(lock->complete_slot); |
|
} |
|
|
|
static int dm_exception_table_init(struct dm_exception_table *et, |
|
uint32_t size, unsigned hash_shift) |
|
{ |
|
unsigned int i; |
|
|
|
et->hash_shift = hash_shift; |
|
et->hash_mask = size - 1; |
|
et->table = dm_vcalloc(size, sizeof(struct hlist_bl_head)); |
|
if (!et->table) |
|
return -ENOMEM; |
|
|
|
for (i = 0; i < size; i++) |
|
INIT_HLIST_BL_HEAD(et->table + i); |
|
|
|
return 0; |
|
} |
|
|
|
static void dm_exception_table_exit(struct dm_exception_table *et, |
|
struct kmem_cache *mem) |
|
{ |
|
struct hlist_bl_head *slot; |
|
struct dm_exception *ex; |
|
struct hlist_bl_node *pos, *n; |
|
int i, size; |
|
|
|
size = et->hash_mask + 1; |
|
for (i = 0; i < size; i++) { |
|
slot = et->table + i; |
|
|
|
hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list) |
|
kmem_cache_free(mem, ex); |
|
} |
|
|
|
vfree(et->table); |
|
} |
|
|
|
static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk) |
|
{ |
|
return (chunk >> et->hash_shift) & et->hash_mask; |
|
} |
|
|
|
static void dm_remove_exception(struct dm_exception *e) |
|
{ |
|
hlist_bl_del(&e->hash_list); |
|
} |
|
|
|
/* |
|
* Return the exception data for a sector, or NULL if not |
|
* remapped. |
|
*/ |
|
static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et, |
|
chunk_t chunk) |
|
{ |
|
struct hlist_bl_head *slot; |
|
struct hlist_bl_node *pos; |
|
struct dm_exception *e; |
|
|
|
slot = &et->table[exception_hash(et, chunk)]; |
|
hlist_bl_for_each_entry(e, pos, slot, hash_list) |
|
if (chunk >= e->old_chunk && |
|
chunk <= e->old_chunk + dm_consecutive_chunk_count(e)) |
|
return e; |
|
|
|
return NULL; |
|
} |
|
|
|
static struct dm_exception *alloc_completed_exception(gfp_t gfp) |
|
{ |
|
struct dm_exception *e; |
|
|
|
e = kmem_cache_alloc(exception_cache, gfp); |
|
if (!e && gfp == GFP_NOIO) |
|
e = kmem_cache_alloc(exception_cache, GFP_ATOMIC); |
|
|
|
return e; |
|
} |
|
|
|
static void free_completed_exception(struct dm_exception *e) |
|
{ |
|
kmem_cache_free(exception_cache, e); |
|
} |
|
|
|
static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s) |
|
{ |
|
struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool, |
|
GFP_NOIO); |
|
|
|
atomic_inc(&s->pending_exceptions_count); |
|
pe->snap = s; |
|
|
|
return pe; |
|
} |
|
|
|
static void free_pending_exception(struct dm_snap_pending_exception *pe) |
|
{ |
|
struct dm_snapshot *s = pe->snap; |
|
|
|
mempool_free(pe, &s->pending_pool); |
|
smp_mb__before_atomic(); |
|
atomic_dec(&s->pending_exceptions_count); |
|
} |
|
|
|
static void dm_insert_exception(struct dm_exception_table *eh, |
|
struct dm_exception *new_e) |
|
{ |
|
struct hlist_bl_head *l; |
|
struct hlist_bl_node *pos; |
|
struct dm_exception *e = NULL; |
|
|
|
l = &eh->table[exception_hash(eh, new_e->old_chunk)]; |
|
|
|
/* Add immediately if this table doesn't support consecutive chunks */ |
|
if (!eh->hash_shift) |
|
goto out; |
|
|
|
/* List is ordered by old_chunk */ |
|
hlist_bl_for_each_entry(e, pos, l, hash_list) { |
|
/* Insert after an existing chunk? */ |
|
if (new_e->old_chunk == (e->old_chunk + |
|
dm_consecutive_chunk_count(e) + 1) && |
|
new_e->new_chunk == (dm_chunk_number(e->new_chunk) + |
|
dm_consecutive_chunk_count(e) + 1)) { |
|
dm_consecutive_chunk_count_inc(e); |
|
free_completed_exception(new_e); |
|
return; |
|
} |
|
|
|
/* Insert before an existing chunk? */ |
|
if (new_e->old_chunk == (e->old_chunk - 1) && |
|
new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) { |
|
dm_consecutive_chunk_count_inc(e); |
|
e->old_chunk--; |
|
e->new_chunk--; |
|
free_completed_exception(new_e); |
|
return; |
|
} |
|
|
|
if (new_e->old_chunk < e->old_chunk) |
|
break; |
|
} |
|
|
|
out: |
|
if (!e) { |
|
/* |
|
* Either the table doesn't support consecutive chunks or slot |
|
* l is empty. |
|
*/ |
|
hlist_bl_add_head(&new_e->hash_list, l); |
|
} else if (new_e->old_chunk < e->old_chunk) { |
|
/* Add before an existing exception */ |
|
hlist_bl_add_before(&new_e->hash_list, &e->hash_list); |
|
} else { |
|
/* Add to l's tail: e is the last exception in this slot */ |
|
hlist_bl_add_behind(&new_e->hash_list, &e->hash_list); |
|
} |
|
} |
|
|
|
/* |
|
* Callback used by the exception stores to load exceptions when |
|
* initialising. |
|
*/ |
|
static int dm_add_exception(void *context, chunk_t old, chunk_t new) |
|
{ |
|
struct dm_exception_table_lock lock; |
|
struct dm_snapshot *s = context; |
|
struct dm_exception *e; |
|
|
|
e = alloc_completed_exception(GFP_KERNEL); |
|
if (!e) |
|
return -ENOMEM; |
|
|
|
e->old_chunk = old; |
|
|
|
/* Consecutive_count is implicitly initialised to zero */ |
|
e->new_chunk = new; |
|
|
|
/* |
|
* Although there is no need to lock access to the exception tables |
|
* here, if we don't then hlist_bl_add_head(), called by |
|
* dm_insert_exception(), will complain about accessing the |
|
* corresponding list without locking it first. |
|
*/ |
|
dm_exception_table_lock_init(s, old, &lock); |
|
|
|
dm_exception_table_lock(&lock); |
|
dm_insert_exception(&s->complete, e); |
|
dm_exception_table_unlock(&lock); |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Return a minimum chunk size of all snapshots that have the specified origin. |
|
* Return zero if the origin has no snapshots. |
|
*/ |
|
static uint32_t __minimum_chunk_size(struct origin *o) |
|
{ |
|
struct dm_snapshot *snap; |
|
unsigned chunk_size = 0; |
|
|
|
if (o) |
|
list_for_each_entry(snap, &o->snapshots, list) |
|
chunk_size = min_not_zero(chunk_size, |
|
snap->store->chunk_size); |
|
|
|
return (uint32_t) chunk_size; |
|
} |
|
|
|
/* |
|
* Hard coded magic. |
|
*/ |
|
static int calc_max_buckets(void) |
|
{ |
|
/* use a fixed size of 2MB */ |
|
unsigned long mem = 2 * 1024 * 1024; |
|
mem /= sizeof(struct hlist_bl_head); |
|
|
|
return mem; |
|
} |
|
|
|
/* |
|
* Allocate room for a suitable hash table. |
|
*/ |
|
static int init_hash_tables(struct dm_snapshot *s) |
|
{ |
|
sector_t hash_size, cow_dev_size, max_buckets; |
|
|
|
/* |
|
* Calculate based on the size of the original volume or |
|
* the COW volume... |
|
*/ |
|
cow_dev_size = get_dev_size(s->cow->bdev); |
|
max_buckets = calc_max_buckets(); |
|
|
|
hash_size = cow_dev_size >> s->store->chunk_shift; |
|
hash_size = min(hash_size, max_buckets); |
|
|
|
if (hash_size < 64) |
|
hash_size = 64; |
|
hash_size = rounddown_pow_of_two(hash_size); |
|
if (dm_exception_table_init(&s->complete, hash_size, |
|
DM_CHUNK_CONSECUTIVE_BITS)) |
|
return -ENOMEM; |
|
|
|
/* |
|
* Allocate hash table for in-flight exceptions |
|
* Make this smaller than the real hash table |
|
*/ |
|
hash_size >>= 3; |
|
if (hash_size < 64) |
|
hash_size = 64; |
|
|
|
if (dm_exception_table_init(&s->pending, hash_size, 0)) { |
|
dm_exception_table_exit(&s->complete, exception_cache); |
|
return -ENOMEM; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static void merge_shutdown(struct dm_snapshot *s) |
|
{ |
|
clear_bit_unlock(RUNNING_MERGE, &s->state_bits); |
|
smp_mb__after_atomic(); |
|
wake_up_bit(&s->state_bits, RUNNING_MERGE); |
|
} |
|
|
|
static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s) |
|
{ |
|
s->first_merging_chunk = 0; |
|
s->num_merging_chunks = 0; |
|
|
|
return bio_list_get(&s->bios_queued_during_merge); |
|
} |
|
|
|
/* |
|
* Remove one chunk from the index of completed exceptions. |
|
*/ |
|
static int __remove_single_exception_chunk(struct dm_snapshot *s, |
|
chunk_t old_chunk) |
|
{ |
|
struct dm_exception *e; |
|
|
|
e = dm_lookup_exception(&s->complete, old_chunk); |
|
if (!e) { |
|
DMERR("Corruption detected: exception for block %llu is " |
|
"on disk but not in memory", |
|
(unsigned long long)old_chunk); |
|
return -EINVAL; |
|
} |
|
|
|
/* |
|
* If this is the only chunk using this exception, remove exception. |
|
*/ |
|
if (!dm_consecutive_chunk_count(e)) { |
|
dm_remove_exception(e); |
|
free_completed_exception(e); |
|
return 0; |
|
} |
|
|
|
/* |
|
* The chunk may be either at the beginning or the end of a |
|
* group of consecutive chunks - never in the middle. We are |
|
* removing chunks in the opposite order to that in which they |
|
* were added, so this should always be true. |
|
* Decrement the consecutive chunk counter and adjust the |
|
* starting point if necessary. |
|
*/ |
|
if (old_chunk == e->old_chunk) { |
|
e->old_chunk++; |
|
e->new_chunk++; |
|
} else if (old_chunk != e->old_chunk + |
|
dm_consecutive_chunk_count(e)) { |
|
DMERR("Attempt to merge block %llu from the " |
|
"middle of a chunk range [%llu - %llu]", |
|
(unsigned long long)old_chunk, |
|
(unsigned long long)e->old_chunk, |
|
(unsigned long long) |
|
e->old_chunk + dm_consecutive_chunk_count(e)); |
|
return -EINVAL; |
|
} |
|
|
|
dm_consecutive_chunk_count_dec(e); |
|
|
|
return 0; |
|
} |
|
|
|
static void flush_bios(struct bio *bio); |
|
|
|
static int remove_single_exception_chunk(struct dm_snapshot *s) |
|
{ |
|
struct bio *b = NULL; |
|
int r; |
|
chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1; |
|
|
|
down_write(&s->lock); |
|
|
|
/* |
|
* Process chunks (and associated exceptions) in reverse order |
|
* so that dm_consecutive_chunk_count_dec() accounting works. |
|
*/ |
|
do { |
|
r = __remove_single_exception_chunk(s, old_chunk); |
|
if (r) |
|
goto out; |
|
} while (old_chunk-- > s->first_merging_chunk); |
|
|
|
b = __release_queued_bios_after_merge(s); |
|
|
|
out: |
|
up_write(&s->lock); |
|
if (b) |
|
flush_bios(b); |
|
|
|
return r; |
|
} |
|
|
|
static int origin_write_extent(struct dm_snapshot *merging_snap, |
|
sector_t sector, unsigned chunk_size); |
|
|
|
static void merge_callback(int read_err, unsigned long write_err, |
|
void *context); |
|
|
|
static uint64_t read_pending_exceptions_done_count(void) |
|
{ |
|
uint64_t pending_exceptions_done; |
|
|
|
spin_lock(&_pending_exceptions_done_spinlock); |
|
pending_exceptions_done = _pending_exceptions_done_count; |
|
spin_unlock(&_pending_exceptions_done_spinlock); |
|
|
|
return pending_exceptions_done; |
|
} |
|
|
|
static void increment_pending_exceptions_done_count(void) |
|
{ |
|
spin_lock(&_pending_exceptions_done_spinlock); |
|
_pending_exceptions_done_count++; |
|
spin_unlock(&_pending_exceptions_done_spinlock); |
|
|
|
wake_up_all(&_pending_exceptions_done); |
|
} |
|
|
|
static void snapshot_merge_next_chunks(struct dm_snapshot *s) |
|
{ |
|
int i, linear_chunks; |
|
chunk_t old_chunk, new_chunk; |
|
struct dm_io_region src, dest; |
|
sector_t io_size; |
|
uint64_t previous_count; |
|
|
|
BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits)); |
|
if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits))) |
|
goto shut; |
|
|
|
/* |
|
* valid flag never changes during merge, so no lock required. |
|
*/ |
|
if (!s->valid) { |
|
DMERR("Snapshot is invalid: can't merge"); |
|
goto shut; |
|
} |
|
|
|
linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk, |
|
&new_chunk); |
|
if (linear_chunks <= 0) { |
|
if (linear_chunks < 0) { |
|
DMERR("Read error in exception store: " |
|
"shutting down merge"); |
|
down_write(&s->lock); |
|
s->merge_failed = true; |
|
up_write(&s->lock); |
|
} |
|
goto shut; |
|
} |
|
|
|
/* Adjust old_chunk and new_chunk to reflect start of linear region */ |
|
old_chunk = old_chunk + 1 - linear_chunks; |
|
new_chunk = new_chunk + 1 - linear_chunks; |
|
|
|
/* |
|
* Use one (potentially large) I/O to copy all 'linear_chunks' |
|
* from the exception store to the origin |
|
*/ |
|
io_size = linear_chunks * s->store->chunk_size; |
|
|
|
dest.bdev = s->origin->bdev; |
|
dest.sector = chunk_to_sector(s->store, old_chunk); |
|
dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector); |
|
|
|
src.bdev = s->cow->bdev; |
|
src.sector = chunk_to_sector(s->store, new_chunk); |
|
src.count = dest.count; |
|
|
|
/* |
|
* Reallocate any exceptions needed in other snapshots then |
|
* wait for the pending exceptions to complete. |
|
* Each time any pending exception (globally on the system) |
|
* completes we are woken and repeat the process to find out |
|
* if we can proceed. While this may not seem a particularly |
|
* efficient algorithm, it is not expected to have any |
|
* significant impact on performance. |
|
*/ |
|
previous_count = read_pending_exceptions_done_count(); |
|
while (origin_write_extent(s, dest.sector, io_size)) { |
|
wait_event(_pending_exceptions_done, |
|
(read_pending_exceptions_done_count() != |
|
previous_count)); |
|
/* Retry after the wait, until all exceptions are done. */ |
|
previous_count = read_pending_exceptions_done_count(); |
|
} |
|
|
|
down_write(&s->lock); |
|
s->first_merging_chunk = old_chunk; |
|
s->num_merging_chunks = linear_chunks; |
|
up_write(&s->lock); |
|
|
|
/* Wait until writes to all 'linear_chunks' drain */ |
|
for (i = 0; i < linear_chunks; i++) |
|
__check_for_conflicting_io(s, old_chunk + i); |
|
|
|
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s); |
|
return; |
|
|
|
shut: |
|
merge_shutdown(s); |
|
} |
|
|
|
static void error_bios(struct bio *bio); |
|
|
|
static int flush_data(struct dm_snapshot *s) |
|
{ |
|
struct bio *flush_bio = &s->flush_bio; |
|
|
|
bio_reset(flush_bio); |
|
bio_set_dev(flush_bio, s->origin->bdev); |
|
flush_bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH; |
|
|
|
return submit_bio_wait(flush_bio); |
|
} |
|
|
|
static void merge_callback(int read_err, unsigned long write_err, void *context) |
|
{ |
|
struct dm_snapshot *s = context; |
|
struct bio *b = NULL; |
|
|
|
if (read_err || write_err) { |
|
if (read_err) |
|
DMERR("Read error: shutting down merge."); |
|
else |
|
DMERR("Write error: shutting down merge."); |
|
goto shut; |
|
} |
|
|
|
if (flush_data(s) < 0) { |
|
DMERR("Flush after merge failed: shutting down merge"); |
|
goto shut; |
|
} |
|
|
|
if (s->store->type->commit_merge(s->store, |
|
s->num_merging_chunks) < 0) { |
|
DMERR("Write error in exception store: shutting down merge"); |
|
goto shut; |
|
} |
|
|
|
if (remove_single_exception_chunk(s) < 0) |
|
goto shut; |
|
|
|
snapshot_merge_next_chunks(s); |
|
|
|
return; |
|
|
|
shut: |
|
down_write(&s->lock); |
|
s->merge_failed = true; |
|
b = __release_queued_bios_after_merge(s); |
|
up_write(&s->lock); |
|
error_bios(b); |
|
|
|
merge_shutdown(s); |
|
} |
|
|
|
static void start_merge(struct dm_snapshot *s) |
|
{ |
|
if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits)) |
|
snapshot_merge_next_chunks(s); |
|
} |
|
|
|
/* |
|
* Stop the merging process and wait until it finishes. |
|
*/ |
|
static void stop_merge(struct dm_snapshot *s) |
|
{ |
|
set_bit(SHUTDOWN_MERGE, &s->state_bits); |
|
wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE); |
|
clear_bit(SHUTDOWN_MERGE, &s->state_bits); |
|
} |
|
|
|
static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s, |
|
struct dm_target *ti) |
|
{ |
|
int r; |
|
unsigned argc; |
|
const char *arg_name; |
|
|
|
static const struct dm_arg _args[] = { |
|
{0, 2, "Invalid number of feature arguments"}, |
|
}; |
|
|
|
/* |
|
* No feature arguments supplied. |
|
*/ |
|
if (!as->argc) |
|
return 0; |
|
|
|
r = dm_read_arg_group(_args, as, &argc, &ti->error); |
|
if (r) |
|
return -EINVAL; |
|
|
|
while (argc && !r) { |
|
arg_name = dm_shift_arg(as); |
|
argc--; |
|
|
|
if (!strcasecmp(arg_name, "discard_zeroes_cow")) |
|
s->discard_zeroes_cow = true; |
|
|
|
else if (!strcasecmp(arg_name, "discard_passdown_origin")) |
|
s->discard_passdown_origin = true; |
|
|
|
else { |
|
ti->error = "Unrecognised feature requested"; |
|
r = -EINVAL; |
|
break; |
|
} |
|
} |
|
|
|
if (!s->discard_zeroes_cow && s->discard_passdown_origin) { |
|
/* |
|
* TODO: really these are disjoint.. but ti->num_discard_bios |
|
* and dm_bio_get_target_bio_nr() require rigid constraints. |
|
*/ |
|
ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow"; |
|
r = -EINVAL; |
|
} |
|
|
|
return r; |
|
} |
|
|
|
/* |
|
* Construct a snapshot mapping: |
|
* <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*] |
|
*/ |
|
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) |
|
{ |
|
struct dm_snapshot *s; |
|
struct dm_arg_set as; |
|
int i; |
|
int r = -EINVAL; |
|
char *origin_path, *cow_path; |
|
dev_t origin_dev, cow_dev; |
|
unsigned args_used, num_flush_bios = 1; |
|
fmode_t origin_mode = FMODE_READ; |
|
|
|
if (argc < 4) { |
|
ti->error = "requires 4 or more arguments"; |
|
r = -EINVAL; |
|
goto bad; |
|
} |
|
|
|
if (dm_target_is_snapshot_merge(ti)) { |
|
num_flush_bios = 2; |
|
origin_mode = FMODE_WRITE; |
|
} |
|
|
|
s = kzalloc(sizeof(*s), GFP_KERNEL); |
|
if (!s) { |
|
ti->error = "Cannot allocate private snapshot structure"; |
|
r = -ENOMEM; |
|
goto bad; |
|
} |
|
|
|
as.argc = argc; |
|
as.argv = argv; |
|
dm_consume_args(&as, 4); |
|
r = parse_snapshot_features(&as, s, ti); |
|
if (r) |
|
goto bad_features; |
|
|
|
origin_path = argv[0]; |
|
argv++; |
|
argc--; |
|
|
|
r = dm_get_device(ti, origin_path, origin_mode, &s->origin); |
|
if (r) { |
|
ti->error = "Cannot get origin device"; |
|
goto bad_origin; |
|
} |
|
origin_dev = s->origin->bdev->bd_dev; |
|
|
|
cow_path = argv[0]; |
|
argv++; |
|
argc--; |
|
|
|
cow_dev = dm_get_dev_t(cow_path); |
|
if (cow_dev && cow_dev == origin_dev) { |
|
ti->error = "COW device cannot be the same as origin device"; |
|
r = -EINVAL; |
|
goto bad_cow; |
|
} |
|
|
|
r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow); |
|
if (r) { |
|
ti->error = "Cannot get COW device"; |
|
goto bad_cow; |
|
} |
|
|
|
r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store); |
|
if (r) { |
|
ti->error = "Couldn't create exception store"; |
|
r = -EINVAL; |
|
goto bad_store; |
|
} |
|
|
|
argv += args_used; |
|
argc -= args_used; |
|
|
|
s->ti = ti; |
|
s->valid = 1; |
|
s->snapshot_overflowed = 0; |
|
s->active = 0; |
|
atomic_set(&s->pending_exceptions_count, 0); |
|
spin_lock_init(&s->pe_allocation_lock); |
|
s->exception_start_sequence = 0; |
|
s->exception_complete_sequence = 0; |
|
s->out_of_order_tree = RB_ROOT; |
|
init_rwsem(&s->lock); |
|
INIT_LIST_HEAD(&s->list); |
|
spin_lock_init(&s->pe_lock); |
|
s->state_bits = 0; |
|
s->merge_failed = false; |
|
s->first_merging_chunk = 0; |
|
s->num_merging_chunks = 0; |
|
bio_list_init(&s->bios_queued_during_merge); |
|
bio_init(&s->flush_bio, NULL, 0); |
|
|
|
/* Allocate hash table for COW data */ |
|
if (init_hash_tables(s)) { |
|
ti->error = "Unable to allocate hash table space"; |
|
r = -ENOMEM; |
|
goto bad_hash_tables; |
|
} |
|
|
|
init_waitqueue_head(&s->in_progress_wait); |
|
|
|
s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle); |
|
if (IS_ERR(s->kcopyd_client)) { |
|
r = PTR_ERR(s->kcopyd_client); |
|
ti->error = "Could not create kcopyd client"; |
|
goto bad_kcopyd; |
|
} |
|
|
|
r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache); |
|
if (r) { |
|
ti->error = "Could not allocate mempool for pending exceptions"; |
|
goto bad_pending_pool; |
|
} |
|
|
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) |
|
INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]); |
|
|
|
spin_lock_init(&s->tracked_chunk_lock); |
|
|
|
ti->private = s; |
|
ti->num_flush_bios = num_flush_bios; |
|
if (s->discard_zeroes_cow) |
|
ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1); |
|
ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk); |
|
|
|
/* Add snapshot to the list of snapshots for this origin */ |
|
/* Exceptions aren't triggered till snapshot_resume() is called */ |
|
r = register_snapshot(s); |
|
if (r == -ENOMEM) { |
|
ti->error = "Snapshot origin struct allocation failed"; |
|
goto bad_load_and_register; |
|
} else if (r < 0) { |
|
/* invalid handover, register_snapshot has set ti->error */ |
|
goto bad_load_and_register; |
|
} |
|
|
|
/* |
|
* Metadata must only be loaded into one table at once, so skip this |
|
* if metadata will be handed over during resume. |
|
* Chunk size will be set during the handover - set it to zero to |
|
* ensure it's ignored. |
|
*/ |
|
if (r > 0) { |
|
s->store->chunk_size = 0; |
|
return 0; |
|
} |
|
|
|
r = s->store->type->read_metadata(s->store, dm_add_exception, |
|
(void *)s); |
|
if (r < 0) { |
|
ti->error = "Failed to read snapshot metadata"; |
|
goto bad_read_metadata; |
|
} else if (r > 0) { |
|
s->valid = 0; |
|
DMWARN("Snapshot is marked invalid."); |
|
} |
|
|
|
if (!s->store->chunk_size) { |
|
ti->error = "Chunk size not set"; |
|
goto bad_read_metadata; |
|
} |
|
|
|
r = dm_set_target_max_io_len(ti, s->store->chunk_size); |
|
if (r) |
|
goto bad_read_metadata; |
|
|
|
return 0; |
|
|
|
bad_read_metadata: |
|
unregister_snapshot(s); |
|
bad_load_and_register: |
|
mempool_exit(&s->pending_pool); |
|
bad_pending_pool: |
|
dm_kcopyd_client_destroy(s->kcopyd_client); |
|
bad_kcopyd: |
|
dm_exception_table_exit(&s->pending, pending_cache); |
|
dm_exception_table_exit(&s->complete, exception_cache); |
|
bad_hash_tables: |
|
dm_exception_store_destroy(s->store); |
|
bad_store: |
|
dm_put_device(ti, s->cow); |
|
bad_cow: |
|
dm_put_device(ti, s->origin); |
|
bad_origin: |
|
bad_features: |
|
kfree(s); |
|
bad: |
|
return r; |
|
} |
|
|
|
static void __free_exceptions(struct dm_snapshot *s) |
|
{ |
|
dm_kcopyd_client_destroy(s->kcopyd_client); |
|
s->kcopyd_client = NULL; |
|
|
|
dm_exception_table_exit(&s->pending, pending_cache); |
|
dm_exception_table_exit(&s->complete, exception_cache); |
|
} |
|
|
|
static void __handover_exceptions(struct dm_snapshot *snap_src, |
|
struct dm_snapshot *snap_dest) |
|
{ |
|
union { |
|
struct dm_exception_table table_swap; |
|
struct dm_exception_store *store_swap; |
|
} u; |
|
|
|
/* |
|
* Swap all snapshot context information between the two instances. |
|
*/ |
|
u.table_swap = snap_dest->complete; |
|
snap_dest->complete = snap_src->complete; |
|
snap_src->complete = u.table_swap; |
|
|
|
u.store_swap = snap_dest->store; |
|
snap_dest->store = snap_src->store; |
|
snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow; |
|
snap_src->store = u.store_swap; |
|
|
|
snap_dest->store->snap = snap_dest; |
|
snap_src->store->snap = snap_src; |
|
|
|
snap_dest->ti->max_io_len = snap_dest->store->chunk_size; |
|
snap_dest->valid = snap_src->valid; |
|
snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed; |
|
|
|
/* |
|
* Set source invalid to ensure it receives no further I/O. |
|
*/ |
|
snap_src->valid = 0; |
|
} |
|
|
|
static void snapshot_dtr(struct dm_target *ti) |
|
{ |
|
#ifdef CONFIG_DM_DEBUG |
|
int i; |
|
#endif |
|
struct dm_snapshot *s = ti->private; |
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
|
|
|
down_read(&_origins_lock); |
|
/* Check whether exception handover must be cancelled */ |
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
|
if (snap_src && snap_dest && (s == snap_src)) { |
|
down_write(&snap_dest->lock); |
|
snap_dest->valid = 0; |
|
up_write(&snap_dest->lock); |
|
DMERR("Cancelling snapshot handover."); |
|
} |
|
up_read(&_origins_lock); |
|
|
|
if (dm_target_is_snapshot_merge(ti)) |
|
stop_merge(s); |
|
|
|
/* Prevent further origin writes from using this snapshot. */ |
|
/* After this returns there can be no new kcopyd jobs. */ |
|
unregister_snapshot(s); |
|
|
|
while (atomic_read(&s->pending_exceptions_count)) |
|
msleep(1); |
|
/* |
|
* Ensure instructions in mempool_exit aren't reordered |
|
* before atomic_read. |
|
*/ |
|
smp_mb(); |
|
|
|
#ifdef CONFIG_DM_DEBUG |
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++) |
|
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i])); |
|
#endif |
|
|
|
__free_exceptions(s); |
|
|
|
mempool_exit(&s->pending_pool); |
|
|
|
dm_exception_store_destroy(s->store); |
|
|
|
bio_uninit(&s->flush_bio); |
|
|
|
dm_put_device(ti, s->cow); |
|
|
|
dm_put_device(ti, s->origin); |
|
|
|
WARN_ON(s->in_progress); |
|
|
|
kfree(s); |
|
} |
|
|
|
static void account_start_copy(struct dm_snapshot *s) |
|
{ |
|
spin_lock(&s->in_progress_wait.lock); |
|
s->in_progress++; |
|
spin_unlock(&s->in_progress_wait.lock); |
|
} |
|
|
|
static void account_end_copy(struct dm_snapshot *s) |
|
{ |
|
spin_lock(&s->in_progress_wait.lock); |
|
BUG_ON(!s->in_progress); |
|
s->in_progress--; |
|
if (likely(s->in_progress <= cow_threshold) && |
|
unlikely(waitqueue_active(&s->in_progress_wait))) |
|
wake_up_locked(&s->in_progress_wait); |
|
spin_unlock(&s->in_progress_wait.lock); |
|
} |
|
|
|
static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins) |
|
{ |
|
if (unlikely(s->in_progress > cow_threshold)) { |
|
spin_lock(&s->in_progress_wait.lock); |
|
if (likely(s->in_progress > cow_threshold)) { |
|
/* |
|
* NOTE: this throttle doesn't account for whether |
|
* the caller is servicing an IO that will trigger a COW |
|
* so excess throttling may result for chunks not required |
|
* to be COW'd. But if cow_threshold was reached, extra |
|
* throttling is unlikely to negatively impact performance. |
|
*/ |
|
DECLARE_WAITQUEUE(wait, current); |
|
__add_wait_queue(&s->in_progress_wait, &wait); |
|
__set_current_state(TASK_UNINTERRUPTIBLE); |
|
spin_unlock(&s->in_progress_wait.lock); |
|
if (unlock_origins) |
|
up_read(&_origins_lock); |
|
io_schedule(); |
|
remove_wait_queue(&s->in_progress_wait, &wait); |
|
return false; |
|
} |
|
spin_unlock(&s->in_progress_wait.lock); |
|
} |
|
return true; |
|
} |
|
|
|
/* |
|
* Flush a list of buffers. |
|
*/ |
|
static void flush_bios(struct bio *bio) |
|
{ |
|
struct bio *n; |
|
|
|
while (bio) { |
|
n = bio->bi_next; |
|
bio->bi_next = NULL; |
|
submit_bio_noacct(bio); |
|
bio = n; |
|
} |
|
} |
|
|
|
static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit); |
|
|
|
/* |
|
* Flush a list of buffers. |
|
*/ |
|
static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio) |
|
{ |
|
struct bio *n; |
|
int r; |
|
|
|
while (bio) { |
|
n = bio->bi_next; |
|
bio->bi_next = NULL; |
|
r = do_origin(s->origin, bio, false); |
|
if (r == DM_MAPIO_REMAPPED) |
|
submit_bio_noacct(bio); |
|
bio = n; |
|
} |
|
} |
|
|
|
/* |
|
* Error a list of buffers. |
|
*/ |
|
static void error_bios(struct bio *bio) |
|
{ |
|
struct bio *n; |
|
|
|
while (bio) { |
|
n = bio->bi_next; |
|
bio->bi_next = NULL; |
|
bio_io_error(bio); |
|
bio = n; |
|
} |
|
} |
|
|
|
static void __invalidate_snapshot(struct dm_snapshot *s, int err) |
|
{ |
|
if (!s->valid) |
|
return; |
|
|
|
if (err == -EIO) |
|
DMERR("Invalidating snapshot: Error reading/writing."); |
|
else if (err == -ENOMEM) |
|
DMERR("Invalidating snapshot: Unable to allocate exception."); |
|
|
|
if (s->store->type->drop_snapshot) |
|
s->store->type->drop_snapshot(s->store); |
|
|
|
s->valid = 0; |
|
|
|
dm_table_event(s->ti->table); |
|
} |
|
|
|
static void invalidate_snapshot(struct dm_snapshot *s, int err) |
|
{ |
|
down_write(&s->lock); |
|
__invalidate_snapshot(s, err); |
|
up_write(&s->lock); |
|
} |
|
|
|
static void pending_complete(void *context, int success) |
|
{ |
|
struct dm_snap_pending_exception *pe = context; |
|
struct dm_exception *e; |
|
struct dm_snapshot *s = pe->snap; |
|
struct bio *origin_bios = NULL; |
|
struct bio *snapshot_bios = NULL; |
|
struct bio *full_bio = NULL; |
|
struct dm_exception_table_lock lock; |
|
int error = 0; |
|
|
|
dm_exception_table_lock_init(s, pe->e.old_chunk, &lock); |
|
|
|
if (!success) { |
|
/* Read/write error - snapshot is unusable */ |
|
invalidate_snapshot(s, -EIO); |
|
error = 1; |
|
|
|
dm_exception_table_lock(&lock); |
|
goto out; |
|
} |
|
|
|
e = alloc_completed_exception(GFP_NOIO); |
|
if (!e) { |
|
invalidate_snapshot(s, -ENOMEM); |
|
error = 1; |
|
|
|
dm_exception_table_lock(&lock); |
|
goto out; |
|
} |
|
*e = pe->e; |
|
|
|
down_read(&s->lock); |
|
dm_exception_table_lock(&lock); |
|
if (!s->valid) { |
|
up_read(&s->lock); |
|
free_completed_exception(e); |
|
error = 1; |
|
|
|
goto out; |
|
} |
|
|
|
/* |
|
* Add a proper exception. After inserting the completed exception all |
|
* subsequent snapshot reads to this chunk will be redirected to the |
|
* COW device. This ensures that we do not starve. Moreover, as long |
|
* as the pending exception exists, neither origin writes nor snapshot |
|
* merging can overwrite the chunk in origin. |
|
*/ |
|
dm_insert_exception(&s->complete, e); |
|
up_read(&s->lock); |
|
|
|
/* Wait for conflicting reads to drain */ |
|
if (__chunk_is_tracked(s, pe->e.old_chunk)) { |
|
dm_exception_table_unlock(&lock); |
|
__check_for_conflicting_io(s, pe->e.old_chunk); |
|
dm_exception_table_lock(&lock); |
|
} |
|
|
|
out: |
|
/* Remove the in-flight exception from the list */ |
|
dm_remove_exception(&pe->e); |
|
|
|
dm_exception_table_unlock(&lock); |
|
|
|
snapshot_bios = bio_list_get(&pe->snapshot_bios); |
|
origin_bios = bio_list_get(&pe->origin_bios); |
|
full_bio = pe->full_bio; |
|
if (full_bio) |
|
full_bio->bi_end_io = pe->full_bio_end_io; |
|
increment_pending_exceptions_done_count(); |
|
|
|
/* Submit any pending write bios */ |
|
if (error) { |
|
if (full_bio) |
|
bio_io_error(full_bio); |
|
error_bios(snapshot_bios); |
|
} else { |
|
if (full_bio) |
|
bio_endio(full_bio); |
|
flush_bios(snapshot_bios); |
|
} |
|
|
|
retry_origin_bios(s, origin_bios); |
|
|
|
free_pending_exception(pe); |
|
} |
|
|
|
static void complete_exception(struct dm_snap_pending_exception *pe) |
|
{ |
|
struct dm_snapshot *s = pe->snap; |
|
|
|
/* Update the metadata if we are persistent */ |
|
s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error, |
|
pending_complete, pe); |
|
} |
|
|
|
/* |
|
* Called when the copy I/O has finished. kcopyd actually runs |
|
* this code so don't block. |
|
*/ |
|
static void copy_callback(int read_err, unsigned long write_err, void *context) |
|
{ |
|
struct dm_snap_pending_exception *pe = context; |
|
struct dm_snapshot *s = pe->snap; |
|
|
|
pe->copy_error = read_err || write_err; |
|
|
|
if (pe->exception_sequence == s->exception_complete_sequence) { |
|
struct rb_node *next; |
|
|
|
s->exception_complete_sequence++; |
|
complete_exception(pe); |
|
|
|
next = rb_first(&s->out_of_order_tree); |
|
while (next) { |
|
pe = rb_entry(next, struct dm_snap_pending_exception, |
|
out_of_order_node); |
|
if (pe->exception_sequence != s->exception_complete_sequence) |
|
break; |
|
next = rb_next(next); |
|
s->exception_complete_sequence++; |
|
rb_erase(&pe->out_of_order_node, &s->out_of_order_tree); |
|
complete_exception(pe); |
|
cond_resched(); |
|
} |
|
} else { |
|
struct rb_node *parent = NULL; |
|
struct rb_node **p = &s->out_of_order_tree.rb_node; |
|
struct dm_snap_pending_exception *pe2; |
|
|
|
while (*p) { |
|
pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node); |
|
parent = *p; |
|
|
|
BUG_ON(pe->exception_sequence == pe2->exception_sequence); |
|
if (pe->exception_sequence < pe2->exception_sequence) |
|
p = &((*p)->rb_left); |
|
else |
|
p = &((*p)->rb_right); |
|
} |
|
|
|
rb_link_node(&pe->out_of_order_node, parent, p); |
|
rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree); |
|
} |
|
account_end_copy(s); |
|
} |
|
|
|
/* |
|
* Dispatches the copy operation to kcopyd. |
|
*/ |
|
static void start_copy(struct dm_snap_pending_exception *pe) |
|
{ |
|
struct dm_snapshot *s = pe->snap; |
|
struct dm_io_region src, dest; |
|
struct block_device *bdev = s->origin->bdev; |
|
sector_t dev_size; |
|
|
|
dev_size = get_dev_size(bdev); |
|
|
|
src.bdev = bdev; |
|
src.sector = chunk_to_sector(s->store, pe->e.old_chunk); |
|
src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector); |
|
|
|
dest.bdev = s->cow->bdev; |
|
dest.sector = chunk_to_sector(s->store, pe->e.new_chunk); |
|
dest.count = src.count; |
|
|
|
/* Hand over to kcopyd */ |
|
account_start_copy(s); |
|
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe); |
|
} |
|
|
|
static void full_bio_end_io(struct bio *bio) |
|
{ |
|
void *callback_data = bio->bi_private; |
|
|
|
dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0); |
|
} |
|
|
|
static void start_full_bio(struct dm_snap_pending_exception *pe, |
|
struct bio *bio) |
|
{ |
|
struct dm_snapshot *s = pe->snap; |
|
void *callback_data; |
|
|
|
pe->full_bio = bio; |
|
pe->full_bio_end_io = bio->bi_end_io; |
|
|
|
account_start_copy(s); |
|
callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client, |
|
copy_callback, pe); |
|
|
|
bio->bi_end_io = full_bio_end_io; |
|
bio->bi_private = callback_data; |
|
|
|
submit_bio_noacct(bio); |
|
} |
|
|
|
static struct dm_snap_pending_exception * |
|
__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk) |
|
{ |
|
struct dm_exception *e = dm_lookup_exception(&s->pending, chunk); |
|
|
|
if (!e) |
|
return NULL; |
|
|
|
return container_of(e, struct dm_snap_pending_exception, e); |
|
} |
|
|
|
/* |
|
* Inserts a pending exception into the pending table. |
|
* |
|
* NOTE: a write lock must be held on the chunk's pending exception table slot |
|
* before calling this. |
|
*/ |
|
static struct dm_snap_pending_exception * |
|
__insert_pending_exception(struct dm_snapshot *s, |
|
struct dm_snap_pending_exception *pe, chunk_t chunk) |
|
{ |
|
pe->e.old_chunk = chunk; |
|
bio_list_init(&pe->origin_bios); |
|
bio_list_init(&pe->snapshot_bios); |
|
pe->started = 0; |
|
pe->full_bio = NULL; |
|
|
|
spin_lock(&s->pe_allocation_lock); |
|
if (s->store->type->prepare_exception(s->store, &pe->e)) { |
|
spin_unlock(&s->pe_allocation_lock); |
|
free_pending_exception(pe); |
|
return NULL; |
|
} |
|
|
|
pe->exception_sequence = s->exception_start_sequence++; |
|
spin_unlock(&s->pe_allocation_lock); |
|
|
|
dm_insert_exception(&s->pending, &pe->e); |
|
|
|
return pe; |
|
} |
|
|
|
/* |
|
* Looks to see if this snapshot already has a pending exception |
|
* for this chunk, otherwise it allocates a new one and inserts |
|
* it into the pending table. |
|
* |
|
* NOTE: a write lock must be held on the chunk's pending exception table slot |
|
* before calling this. |
|
*/ |
|
static struct dm_snap_pending_exception * |
|
__find_pending_exception(struct dm_snapshot *s, |
|
struct dm_snap_pending_exception *pe, chunk_t chunk) |
|
{ |
|
struct dm_snap_pending_exception *pe2; |
|
|
|
pe2 = __lookup_pending_exception(s, chunk); |
|
if (pe2) { |
|
free_pending_exception(pe); |
|
return pe2; |
|
} |
|
|
|
return __insert_pending_exception(s, pe, chunk); |
|
} |
|
|
|
static void remap_exception(struct dm_snapshot *s, struct dm_exception *e, |
|
struct bio *bio, chunk_t chunk) |
|
{ |
|
bio_set_dev(bio, s->cow->bdev); |
|
bio->bi_iter.bi_sector = |
|
chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) + |
|
(chunk - e->old_chunk)) + |
|
(bio->bi_iter.bi_sector & s->store->chunk_mask); |
|
} |
|
|
|
static void zero_callback(int read_err, unsigned long write_err, void *context) |
|
{ |
|
struct bio *bio = context; |
|
struct dm_snapshot *s = bio->bi_private; |
|
|
|
account_end_copy(s); |
|
bio->bi_status = write_err ? BLK_STS_IOERR : 0; |
|
bio_endio(bio); |
|
} |
|
|
|
static void zero_exception(struct dm_snapshot *s, struct dm_exception *e, |
|
struct bio *bio, chunk_t chunk) |
|
{ |
|
struct dm_io_region dest; |
|
|
|
dest.bdev = s->cow->bdev; |
|
dest.sector = bio->bi_iter.bi_sector; |
|
dest.count = s->store->chunk_size; |
|
|
|
account_start_copy(s); |
|
WARN_ON_ONCE(bio->bi_private); |
|
bio->bi_private = s; |
|
dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio); |
|
} |
|
|
|
static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio) |
|
{ |
|
return bio->bi_iter.bi_size == |
|
(s->store->chunk_size << SECTOR_SHIFT); |
|
} |
|
|
|
static int snapshot_map(struct dm_target *ti, struct bio *bio) |
|
{ |
|
struct dm_exception *e; |
|
struct dm_snapshot *s = ti->private; |
|
int r = DM_MAPIO_REMAPPED; |
|
chunk_t chunk; |
|
struct dm_snap_pending_exception *pe = NULL; |
|
struct dm_exception_table_lock lock; |
|
|
|
init_tracked_chunk(bio); |
|
|
|
if (bio->bi_opf & REQ_PREFLUSH) { |
|
bio_set_dev(bio, s->cow->bdev); |
|
return DM_MAPIO_REMAPPED; |
|
} |
|
|
|
chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); |
|
dm_exception_table_lock_init(s, chunk, &lock); |
|
|
|
/* Full snapshots are not usable */ |
|
/* To get here the table must be live so s->active is always set. */ |
|
if (!s->valid) |
|
return DM_MAPIO_KILL; |
|
|
|
if (bio_data_dir(bio) == WRITE) { |
|
while (unlikely(!wait_for_in_progress(s, false))) |
|
; /* wait_for_in_progress() has slept */ |
|
} |
|
|
|
down_read(&s->lock); |
|
dm_exception_table_lock(&lock); |
|
|
|
if (!s->valid || (unlikely(s->snapshot_overflowed) && |
|
bio_data_dir(bio) == WRITE)) { |
|
r = DM_MAPIO_KILL; |
|
goto out_unlock; |
|
} |
|
|
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { |
|
if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) { |
|
/* |
|
* passdown discard to origin (without triggering |
|
* snapshot exceptions via do_origin; doing so would |
|
* defeat the goal of freeing space in origin that is |
|
* implied by the "discard_passdown_origin" feature) |
|
*/ |
|
bio_set_dev(bio, s->origin->bdev); |
|
track_chunk(s, bio, chunk); |
|
goto out_unlock; |
|
} |
|
/* discard to snapshot (target_bio_nr == 0) zeroes exceptions */ |
|
} |
|
|
|
/* If the block is already remapped - use that, else remap it */ |
|
e = dm_lookup_exception(&s->complete, chunk); |
|
if (e) { |
|
remap_exception(s, e, bio, chunk); |
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD) && |
|
io_overlaps_chunk(s, bio)) { |
|
dm_exception_table_unlock(&lock); |
|
up_read(&s->lock); |
|
zero_exception(s, e, bio, chunk); |
|
r = DM_MAPIO_SUBMITTED; /* discard is not issued */ |
|
goto out; |
|
} |
|
goto out_unlock; |
|
} |
|
|
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { |
|
/* |
|
* If no exception exists, complete discard immediately |
|
* otherwise it'll trigger copy-out. |
|
*/ |
|
bio_endio(bio); |
|
r = DM_MAPIO_SUBMITTED; |
|
goto out_unlock; |
|
} |
|
|
|
/* |
|
* Write to snapshot - higher level takes care of RW/RO |
|
* flags so we should only get this if we are |
|
* writeable. |
|
*/ |
|
if (bio_data_dir(bio) == WRITE) { |
|
pe = __lookup_pending_exception(s, chunk); |
|
if (!pe) { |
|
dm_exception_table_unlock(&lock); |
|
pe = alloc_pending_exception(s); |
|
dm_exception_table_lock(&lock); |
|
|
|
e = dm_lookup_exception(&s->complete, chunk); |
|
if (e) { |
|
free_pending_exception(pe); |
|
remap_exception(s, e, bio, chunk); |
|
goto out_unlock; |
|
} |
|
|
|
pe = __find_pending_exception(s, pe, chunk); |
|
if (!pe) { |
|
dm_exception_table_unlock(&lock); |
|
up_read(&s->lock); |
|
|
|
down_write(&s->lock); |
|
|
|
if (s->store->userspace_supports_overflow) { |
|
if (s->valid && !s->snapshot_overflowed) { |
|
s->snapshot_overflowed = 1; |
|
DMERR("Snapshot overflowed: Unable to allocate exception."); |
|
} |
|
} else |
|
__invalidate_snapshot(s, -ENOMEM); |
|
up_write(&s->lock); |
|
|
|
r = DM_MAPIO_KILL; |
|
goto out; |
|
} |
|
} |
|
|
|
remap_exception(s, &pe->e, bio, chunk); |
|
|
|
r = DM_MAPIO_SUBMITTED; |
|
|
|
if (!pe->started && io_overlaps_chunk(s, bio)) { |
|
pe->started = 1; |
|
|
|
dm_exception_table_unlock(&lock); |
|
up_read(&s->lock); |
|
|
|
start_full_bio(pe, bio); |
|
goto out; |
|
} |
|
|
|
bio_list_add(&pe->snapshot_bios, bio); |
|
|
|
if (!pe->started) { |
|
/* this is protected by the exception table lock */ |
|
pe->started = 1; |
|
|
|
dm_exception_table_unlock(&lock); |
|
up_read(&s->lock); |
|
|
|
start_copy(pe); |
|
goto out; |
|
} |
|
} else { |
|
bio_set_dev(bio, s->origin->bdev); |
|
track_chunk(s, bio, chunk); |
|
} |
|
|
|
out_unlock: |
|
dm_exception_table_unlock(&lock); |
|
up_read(&s->lock); |
|
out: |
|
return r; |
|
} |
|
|
|
/* |
|
* A snapshot-merge target behaves like a combination of a snapshot |
|
* target and a snapshot-origin target. It only generates new |
|
* exceptions in other snapshots and not in the one that is being |
|
* merged. |
|
* |
|
* For each chunk, if there is an existing exception, it is used to |
|
* redirect I/O to the cow device. Otherwise I/O is sent to the origin, |
|
* which in turn might generate exceptions in other snapshots. |
|
* If merging is currently taking place on the chunk in question, the |
|
* I/O is deferred by adding it to s->bios_queued_during_merge. |
|
*/ |
|
static int snapshot_merge_map(struct dm_target *ti, struct bio *bio) |
|
{ |
|
struct dm_exception *e; |
|
struct dm_snapshot *s = ti->private; |
|
int r = DM_MAPIO_REMAPPED; |
|
chunk_t chunk; |
|
|
|
init_tracked_chunk(bio); |
|
|
|
if (bio->bi_opf & REQ_PREFLUSH) { |
|
if (!dm_bio_get_target_bio_nr(bio)) |
|
bio_set_dev(bio, s->origin->bdev); |
|
else |
|
bio_set_dev(bio, s->cow->bdev); |
|
return DM_MAPIO_REMAPPED; |
|
} |
|
|
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) { |
|
/* Once merging, discards no longer effect change */ |
|
bio_endio(bio); |
|
return DM_MAPIO_SUBMITTED; |
|
} |
|
|
|
chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector); |
|
|
|
down_write(&s->lock); |
|
|
|
/* Full merging snapshots are redirected to the origin */ |
|
if (!s->valid) |
|
goto redirect_to_origin; |
|
|
|
/* If the block is already remapped - use that */ |
|
e = dm_lookup_exception(&s->complete, chunk); |
|
if (e) { |
|
/* Queue writes overlapping with chunks being merged */ |
|
if (bio_data_dir(bio) == WRITE && |
|
chunk >= s->first_merging_chunk && |
|
chunk < (s->first_merging_chunk + |
|
s->num_merging_chunks)) { |
|
bio_set_dev(bio, s->origin->bdev); |
|
bio_list_add(&s->bios_queued_during_merge, bio); |
|
r = DM_MAPIO_SUBMITTED; |
|
goto out_unlock; |
|
} |
|
|
|
remap_exception(s, e, bio, chunk); |
|
|
|
if (bio_data_dir(bio) == WRITE) |
|
track_chunk(s, bio, chunk); |
|
goto out_unlock; |
|
} |
|
|
|
redirect_to_origin: |
|
bio_set_dev(bio, s->origin->bdev); |
|
|
|
if (bio_data_dir(bio) == WRITE) { |
|
up_write(&s->lock); |
|
return do_origin(s->origin, bio, false); |
|
} |
|
|
|
out_unlock: |
|
up_write(&s->lock); |
|
|
|
return r; |
|
} |
|
|
|
static int snapshot_end_io(struct dm_target *ti, struct bio *bio, |
|
blk_status_t *error) |
|
{ |
|
struct dm_snapshot *s = ti->private; |
|
|
|
if (is_bio_tracked(bio)) |
|
stop_tracking_chunk(s, bio); |
|
|
|
return DM_ENDIO_DONE; |
|
} |
|
|
|
static void snapshot_merge_presuspend(struct dm_target *ti) |
|
{ |
|
struct dm_snapshot *s = ti->private; |
|
|
|
stop_merge(s); |
|
} |
|
|
|
static int snapshot_preresume(struct dm_target *ti) |
|
{ |
|
int r = 0; |
|
struct dm_snapshot *s = ti->private; |
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
|
|
|
down_read(&_origins_lock); |
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
|
if (snap_src && snap_dest) { |
|
down_read(&snap_src->lock); |
|
if (s == snap_src) { |
|
DMERR("Unable to resume snapshot source until " |
|
"handover completes."); |
|
r = -EINVAL; |
|
} else if (!dm_suspended(snap_src->ti)) { |
|
DMERR("Unable to perform snapshot handover until " |
|
"source is suspended."); |
|
r = -EINVAL; |
|
} |
|
up_read(&snap_src->lock); |
|
} |
|
up_read(&_origins_lock); |
|
|
|
return r; |
|
} |
|
|
|
static void snapshot_resume(struct dm_target *ti) |
|
{ |
|
struct dm_snapshot *s = ti->private; |
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL; |
|
struct dm_origin *o; |
|
struct mapped_device *origin_md = NULL; |
|
bool must_restart_merging = false; |
|
|
|
down_read(&_origins_lock); |
|
|
|
o = __lookup_dm_origin(s->origin->bdev); |
|
if (o) |
|
origin_md = dm_table_get_md(o->ti->table); |
|
if (!origin_md) { |
|
(void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging); |
|
if (snap_merging) |
|
origin_md = dm_table_get_md(snap_merging->ti->table); |
|
} |
|
if (origin_md == dm_table_get_md(ti->table)) |
|
origin_md = NULL; |
|
if (origin_md) { |
|
if (dm_hold(origin_md)) |
|
origin_md = NULL; |
|
} |
|
|
|
up_read(&_origins_lock); |
|
|
|
if (origin_md) { |
|
dm_internal_suspend_fast(origin_md); |
|
if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) { |
|
must_restart_merging = true; |
|
stop_merge(snap_merging); |
|
} |
|
} |
|
|
|
down_read(&_origins_lock); |
|
|
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); |
|
if (snap_src && snap_dest) { |
|
down_write(&snap_src->lock); |
|
down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING); |
|
__handover_exceptions(snap_src, snap_dest); |
|
up_write(&snap_dest->lock); |
|
up_write(&snap_src->lock); |
|
} |
|
|
|
up_read(&_origins_lock); |
|
|
|
if (origin_md) { |
|
if (must_restart_merging) |
|
start_merge(snap_merging); |
|
dm_internal_resume_fast(origin_md); |
|
dm_put(origin_md); |
|
} |
|
|
|
/* Now we have correct chunk size, reregister */ |
|
reregister_snapshot(s); |
|
|
|
down_write(&s->lock); |
|
s->active = 1; |
|
up_write(&s->lock); |
|
} |
|
|
|
static uint32_t get_origin_minimum_chunksize(struct block_device *bdev) |
|
{ |
|
uint32_t min_chunksize; |
|
|
|
down_read(&_origins_lock); |
|
min_chunksize = __minimum_chunk_size(__lookup_origin(bdev)); |
|
up_read(&_origins_lock); |
|
|
|
return min_chunksize; |
|
} |
|
|
|
static void snapshot_merge_resume(struct dm_target *ti) |
|
{ |
|
struct dm_snapshot *s = ti->private; |
|
|
|
/* |
|
* Handover exceptions from existing snapshot. |
|
*/ |
|
snapshot_resume(ti); |
|
|
|
/* |
|
* snapshot-merge acts as an origin, so set ti->max_io_len |
|
*/ |
|
ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev); |
|
|
|
start_merge(s); |
|
} |
|
|
|
static void snapshot_status(struct dm_target *ti, status_type_t type, |
|
unsigned status_flags, char *result, unsigned maxlen) |
|
{ |
|
unsigned sz = 0; |
|
struct dm_snapshot *snap = ti->private; |
|
unsigned num_features; |
|
|
|
switch (type) { |
|
case STATUSTYPE_INFO: |
|
|
|
down_write(&snap->lock); |
|
|
|
if (!snap->valid) |
|
DMEMIT("Invalid"); |
|
else if (snap->merge_failed) |
|
DMEMIT("Merge failed"); |
|
else if (snap->snapshot_overflowed) |
|
DMEMIT("Overflow"); |
|
else { |
|
if (snap->store->type->usage) { |
|
sector_t total_sectors, sectors_allocated, |
|
metadata_sectors; |
|
snap->store->type->usage(snap->store, |
|
&total_sectors, |
|
§ors_allocated, |
|
&metadata_sectors); |
|
DMEMIT("%llu/%llu %llu", |
|
(unsigned long long)sectors_allocated, |
|
(unsigned long long)total_sectors, |
|
(unsigned long long)metadata_sectors); |
|
} |
|
else |
|
DMEMIT("Unknown"); |
|
} |
|
|
|
up_write(&snap->lock); |
|
|
|
break; |
|
|
|
case STATUSTYPE_TABLE: |
|
/* |
|
* kdevname returns a static pointer so we need |
|
* to make private copies if the output is to |
|
* make sense. |
|
*/ |
|
DMEMIT("%s %s", snap->origin->name, snap->cow->name); |
|
sz += snap->store->type->status(snap->store, type, result + sz, |
|
maxlen - sz); |
|
num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin; |
|
if (num_features) { |
|
DMEMIT(" %u", num_features); |
|
if (snap->discard_zeroes_cow) |
|
DMEMIT(" discard_zeroes_cow"); |
|
if (snap->discard_passdown_origin) |
|
DMEMIT(" discard_passdown_origin"); |
|
} |
|
break; |
|
} |
|
} |
|
|
|
static int snapshot_iterate_devices(struct dm_target *ti, |
|
iterate_devices_callout_fn fn, void *data) |
|
{ |
|
struct dm_snapshot *snap = ti->private; |
|
int r; |
|
|
|
r = fn(ti, snap->origin, 0, ti->len, data); |
|
|
|
if (!r) |
|
r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data); |
|
|
|
return r; |
|
} |
|
|
|
static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits) |
|
{ |
|
struct dm_snapshot *snap = ti->private; |
|
|
|
if (snap->discard_zeroes_cow) { |
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; |
|
|
|
down_read(&_origins_lock); |
|
|
|
(void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL); |
|
if (snap_src && snap_dest) |
|
snap = snap_src; |
|
|
|
/* All discards are split on chunk_size boundary */ |
|
limits->discard_granularity = snap->store->chunk_size; |
|
limits->max_discard_sectors = snap->store->chunk_size; |
|
|
|
up_read(&_origins_lock); |
|
} |
|
} |
|
|
|
/*----------------------------------------------------------------- |
|
* Origin methods |
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*---------------------------------------------------------------*/ |
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|
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/* |
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* If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any |
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* supplied bio was ignored. The caller may submit it immediately. |
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* (No remapping actually occurs as the origin is always a direct linear |
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* map.) |
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* |
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* If further exceptions are required, DM_MAPIO_SUBMITTED is returned |
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* and any supplied bio is added to a list to be submitted once all |
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* the necessary exceptions exist. |
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*/ |
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static int __origin_write(struct list_head *snapshots, sector_t sector, |
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struct bio *bio) |
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{ |
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int r = DM_MAPIO_REMAPPED; |
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struct dm_snapshot *snap; |
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struct dm_exception *e; |
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struct dm_snap_pending_exception *pe, *pe2; |
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struct dm_snap_pending_exception *pe_to_start_now = NULL; |
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struct dm_snap_pending_exception *pe_to_start_last = NULL; |
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struct dm_exception_table_lock lock; |
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chunk_t chunk; |
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|
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/* Do all the snapshots on this origin */ |
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list_for_each_entry (snap, snapshots, list) { |
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/* |
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* Don't make new exceptions in a merging snapshot |
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* because it has effectively been deleted |
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*/ |
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if (dm_target_is_snapshot_merge(snap->ti)) |
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continue; |
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|
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/* Nothing to do if writing beyond end of snapshot */ |
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if (sector >= dm_table_get_size(snap->ti->table)) |
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continue; |
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|
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/* |
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* Remember, different snapshots can have |
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* different chunk sizes. |
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*/ |
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chunk = sector_to_chunk(snap->store, sector); |
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dm_exception_table_lock_init(snap, chunk, &lock); |
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|
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down_read(&snap->lock); |
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dm_exception_table_lock(&lock); |
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|
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/* Only deal with valid and active snapshots */ |
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if (!snap->valid || !snap->active) |
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goto next_snapshot; |
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|
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pe = __lookup_pending_exception(snap, chunk); |
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if (!pe) { |
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/* |
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* Check exception table to see if block is already |
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* remapped in this snapshot and trigger an exception |
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* if not. |
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*/ |
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e = dm_lookup_exception(&snap->complete, chunk); |
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if (e) |
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goto next_snapshot; |
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|
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dm_exception_table_unlock(&lock); |
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pe = alloc_pending_exception(snap); |
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dm_exception_table_lock(&lock); |
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|
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pe2 = __lookup_pending_exception(snap, chunk); |
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|
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if (!pe2) { |
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e = dm_lookup_exception(&snap->complete, chunk); |
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if (e) { |
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free_pending_exception(pe); |
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goto next_snapshot; |
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} |
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|
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pe = __insert_pending_exception(snap, pe, chunk); |
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if (!pe) { |
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dm_exception_table_unlock(&lock); |
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up_read(&snap->lock); |
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|
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invalidate_snapshot(snap, -ENOMEM); |
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continue; |
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} |
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} else { |
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free_pending_exception(pe); |
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pe = pe2; |
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} |
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} |
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|
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r = DM_MAPIO_SUBMITTED; |
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|
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/* |
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* If an origin bio was supplied, queue it to wait for the |
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* completion of this exception, and start this one last, |
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* at the end of the function. |
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*/ |
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if (bio) { |
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bio_list_add(&pe->origin_bios, bio); |
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bio = NULL; |
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|
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if (!pe->started) { |
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pe->started = 1; |
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pe_to_start_last = pe; |
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} |
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} |
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if (!pe->started) { |
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pe->started = 1; |
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pe_to_start_now = pe; |
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} |
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next_snapshot: |
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dm_exception_table_unlock(&lock); |
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up_read(&snap->lock); |
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if (pe_to_start_now) { |
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start_copy(pe_to_start_now); |
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pe_to_start_now = NULL; |
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} |
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} |
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|
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/* |
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* Submit the exception against which the bio is queued last, |
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* to give the other exceptions a head start. |
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*/ |
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if (pe_to_start_last) |
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start_copy(pe_to_start_last); |
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|
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return r; |
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} |
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|
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/* |
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* Called on a write from the origin driver. |
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*/ |
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static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit) |
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{ |
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struct origin *o; |
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int r = DM_MAPIO_REMAPPED; |
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|
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again: |
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down_read(&_origins_lock); |
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o = __lookup_origin(origin->bdev); |
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if (o) { |
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if (limit) { |
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struct dm_snapshot *s; |
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list_for_each_entry(s, &o->snapshots, list) |
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if (unlikely(!wait_for_in_progress(s, true))) |
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goto again; |
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} |
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r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio); |
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} |
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up_read(&_origins_lock); |
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return r; |
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} |
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|
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/* |
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* Trigger exceptions in all non-merging snapshots. |
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* |
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* The chunk size of the merging snapshot may be larger than the chunk |
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* size of some other snapshot so we may need to reallocate multiple |
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* chunks in other snapshots. |
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* |
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* We scan all the overlapping exceptions in the other snapshots. |
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* Returns 1 if anything was reallocated and must be waited for, |
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* otherwise returns 0. |
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* |
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* size must be a multiple of merging_snap's chunk_size. |
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*/ |
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static int origin_write_extent(struct dm_snapshot *merging_snap, |
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sector_t sector, unsigned size) |
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{ |
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int must_wait = 0; |
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sector_t n; |
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struct origin *o; |
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|
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/* |
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* The origin's __minimum_chunk_size() got stored in max_io_len |
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* by snapshot_merge_resume(). |
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*/ |
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down_read(&_origins_lock); |
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o = __lookup_origin(merging_snap->origin->bdev); |
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for (n = 0; n < size; n += merging_snap->ti->max_io_len) |
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if (__origin_write(&o->snapshots, sector + n, NULL) == |
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DM_MAPIO_SUBMITTED) |
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must_wait = 1; |
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up_read(&_origins_lock); |
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|
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return must_wait; |
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} |
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|
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/* |
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* Origin: maps a linear range of a device, with hooks for snapshotting. |
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*/ |
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|
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/* |
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* Construct an origin mapping: <dev_path> |
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* The context for an origin is merely a 'struct dm_dev *' |
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* pointing to the real device. |
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*/ |
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static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv) |
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{ |
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int r; |
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struct dm_origin *o; |
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|
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if (argc != 1) { |
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ti->error = "origin: incorrect number of arguments"; |
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return -EINVAL; |
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} |
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|
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o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL); |
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if (!o) { |
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ti->error = "Cannot allocate private origin structure"; |
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r = -ENOMEM; |
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goto bad_alloc; |
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} |
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r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev); |
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if (r) { |
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ti->error = "Cannot get target device"; |
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goto bad_open; |
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} |
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o->ti = ti; |
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ti->private = o; |
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ti->num_flush_bios = 1; |
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return 0; |
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bad_open: |
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kfree(o); |
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bad_alloc: |
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return r; |
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} |
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|
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static void origin_dtr(struct dm_target *ti) |
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{ |
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struct dm_origin *o = ti->private; |
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|
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dm_put_device(ti, o->dev); |
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kfree(o); |
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} |
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|
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static int origin_map(struct dm_target *ti, struct bio *bio) |
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{ |
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struct dm_origin *o = ti->private; |
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unsigned available_sectors; |
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bio_set_dev(bio, o->dev->bdev); |
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if (unlikely(bio->bi_opf & REQ_PREFLUSH)) |
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return DM_MAPIO_REMAPPED; |
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|
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if (bio_data_dir(bio) != WRITE) |
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return DM_MAPIO_REMAPPED; |
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available_sectors = o->split_boundary - |
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((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1)); |
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|
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if (bio_sectors(bio) > available_sectors) |
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dm_accept_partial_bio(bio, available_sectors); |
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|
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/* Only tell snapshots if this is a write */ |
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return do_origin(o->dev, bio, true); |
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} |
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|
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/* |
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* Set the target "max_io_len" field to the minimum of all the snapshots' |
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* chunk sizes. |
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*/ |
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static void origin_resume(struct dm_target *ti) |
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{ |
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struct dm_origin *o = ti->private; |
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|
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o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev); |
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|
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down_write(&_origins_lock); |
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__insert_dm_origin(o); |
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up_write(&_origins_lock); |
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} |
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|
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static void origin_postsuspend(struct dm_target *ti) |
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{ |
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struct dm_origin *o = ti->private; |
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|
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down_write(&_origins_lock); |
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__remove_dm_origin(o); |
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up_write(&_origins_lock); |
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} |
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|
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static void origin_status(struct dm_target *ti, status_type_t type, |
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unsigned status_flags, char *result, unsigned maxlen) |
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{ |
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struct dm_origin *o = ti->private; |
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|
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switch (type) { |
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case STATUSTYPE_INFO: |
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result[0] = '\0'; |
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break; |
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|
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case STATUSTYPE_TABLE: |
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snprintf(result, maxlen, "%s", o->dev->name); |
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break; |
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} |
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} |
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|
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static int origin_iterate_devices(struct dm_target *ti, |
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iterate_devices_callout_fn fn, void *data) |
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{ |
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struct dm_origin *o = ti->private; |
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|
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return fn(ti, o->dev, 0, ti->len, data); |
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} |
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|
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static struct target_type origin_target = { |
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.name = "snapshot-origin", |
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.version = {1, 9, 0}, |
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.module = THIS_MODULE, |
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.ctr = origin_ctr, |
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.dtr = origin_dtr, |
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.map = origin_map, |
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.resume = origin_resume, |
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.postsuspend = origin_postsuspend, |
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.status = origin_status, |
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.iterate_devices = origin_iterate_devices, |
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}; |
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|
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static struct target_type snapshot_target = { |
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.name = "snapshot", |
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.version = {1, 16, 0}, |
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.module = THIS_MODULE, |
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.ctr = snapshot_ctr, |
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.dtr = snapshot_dtr, |
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.map = snapshot_map, |
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.end_io = snapshot_end_io, |
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.preresume = snapshot_preresume, |
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.resume = snapshot_resume, |
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.status = snapshot_status, |
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.iterate_devices = snapshot_iterate_devices, |
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.io_hints = snapshot_io_hints, |
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}; |
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|
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static struct target_type merge_target = { |
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.name = dm_snapshot_merge_target_name, |
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.version = {1, 5, 0}, |
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.module = THIS_MODULE, |
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.ctr = snapshot_ctr, |
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.dtr = snapshot_dtr, |
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.map = snapshot_merge_map, |
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.end_io = snapshot_end_io, |
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.presuspend = snapshot_merge_presuspend, |
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.preresume = snapshot_preresume, |
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.resume = snapshot_merge_resume, |
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.status = snapshot_status, |
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.iterate_devices = snapshot_iterate_devices, |
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.io_hints = snapshot_io_hints, |
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}; |
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|
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static int __init dm_snapshot_init(void) |
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{ |
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int r; |
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|
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r = dm_exception_store_init(); |
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if (r) { |
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DMERR("Failed to initialize exception stores"); |
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return r; |
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} |
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|
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r = init_origin_hash(); |
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if (r) { |
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DMERR("init_origin_hash failed."); |
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goto bad_origin_hash; |
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} |
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|
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exception_cache = KMEM_CACHE(dm_exception, 0); |
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if (!exception_cache) { |
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DMERR("Couldn't create exception cache."); |
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r = -ENOMEM; |
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goto bad_exception_cache; |
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} |
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|
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pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0); |
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if (!pending_cache) { |
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DMERR("Couldn't create pending cache."); |
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r = -ENOMEM; |
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goto bad_pending_cache; |
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} |
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|
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r = dm_register_target(&snapshot_target); |
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if (r < 0) { |
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DMERR("snapshot target register failed %d", r); |
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goto bad_register_snapshot_target; |
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} |
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|
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r = dm_register_target(&origin_target); |
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if (r < 0) { |
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DMERR("Origin target register failed %d", r); |
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goto bad_register_origin_target; |
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} |
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|
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r = dm_register_target(&merge_target); |
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if (r < 0) { |
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DMERR("Merge target register failed %d", r); |
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goto bad_register_merge_target; |
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} |
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|
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return 0; |
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|
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bad_register_merge_target: |
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dm_unregister_target(&origin_target); |
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bad_register_origin_target: |
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dm_unregister_target(&snapshot_target); |
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bad_register_snapshot_target: |
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kmem_cache_destroy(pending_cache); |
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bad_pending_cache: |
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kmem_cache_destroy(exception_cache); |
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bad_exception_cache: |
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exit_origin_hash(); |
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bad_origin_hash: |
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dm_exception_store_exit(); |
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|
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return r; |
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} |
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|
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static void __exit dm_snapshot_exit(void) |
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{ |
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dm_unregister_target(&snapshot_target); |
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dm_unregister_target(&origin_target); |
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dm_unregister_target(&merge_target); |
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|
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exit_origin_hash(); |
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kmem_cache_destroy(pending_cache); |
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kmem_cache_destroy(exception_cache); |
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|
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dm_exception_store_exit(); |
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} |
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|
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/* Module hooks */ |
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module_init(dm_snapshot_init); |
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module_exit(dm_snapshot_exit); |
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|
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MODULE_DESCRIPTION(DM_NAME " snapshot target"); |
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MODULE_AUTHOR("Joe Thornber"); |
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MODULE_LICENSE("GPL"); |
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MODULE_ALIAS("dm-snapshot-origin"); |
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MODULE_ALIAS("dm-snapshot-merge");
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