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971 lines
22 KiB
971 lines
22 KiB
/* |
|
* Copyright (C) 2001-2002 Sistina Software (UK) Limited. |
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* Copyright (C) 2006-2008 Red Hat GmbH |
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* |
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* This file is released under the GPL. |
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*/ |
|
|
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#include "dm-exception-store.h" |
|
|
|
#include <linux/ctype.h> |
|
#include <linux/mm.h> |
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#include <linux/pagemap.h> |
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#include <linux/vmalloc.h> |
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#include <linux/export.h> |
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#include <linux/slab.h> |
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#include <linux/dm-io.h> |
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#include <linux/dm-bufio.h> |
|
|
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#define DM_MSG_PREFIX "persistent snapshot" |
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#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32U /* 16KB */ |
|
|
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#define DM_PREFETCH_CHUNKS 12 |
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|
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/*----------------------------------------------------------------- |
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* Persistent snapshots, by persistent we mean that the snapshot |
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* will survive a reboot. |
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*---------------------------------------------------------------*/ |
|
|
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/* |
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* We need to store a record of which parts of the origin have |
|
* been copied to the snapshot device. The snapshot code |
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* requires that we copy exception chunks to chunk aligned areas |
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* of the COW store. It makes sense therefore, to store the |
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* metadata in chunk size blocks. |
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* |
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* There is no backward or forward compatibility implemented, |
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* snapshots with different disk versions than the kernel will |
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* not be usable. It is expected that "lvcreate" will blank out |
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* the start of a fresh COW device before calling the snapshot |
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* constructor. |
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* |
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* The first chunk of the COW device just contains the header. |
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* After this there is a chunk filled with exception metadata, |
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* followed by as many exception chunks as can fit in the |
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* metadata areas. |
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* |
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* All on disk structures are in little-endian format. The end |
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* of the exceptions info is indicated by an exception with a |
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* new_chunk of 0, which is invalid since it would point to the |
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* header chunk. |
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*/ |
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|
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/* |
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* Magic for persistent snapshots: "SnAp" - Feeble isn't it. |
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*/ |
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#define SNAP_MAGIC 0x70416e53 |
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|
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/* |
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* The on-disk version of the metadata. |
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*/ |
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#define SNAPSHOT_DISK_VERSION 1 |
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|
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#define NUM_SNAPSHOT_HDR_CHUNKS 1 |
|
|
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struct disk_header { |
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__le32 magic; |
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|
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/* |
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* Is this snapshot valid. There is no way of recovering |
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* an invalid snapshot. |
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*/ |
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__le32 valid; |
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|
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/* |
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* Simple, incrementing version. no backward |
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* compatibility. |
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*/ |
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__le32 version; |
|
|
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/* In sectors */ |
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__le32 chunk_size; |
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} __packed; |
|
|
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struct disk_exception { |
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__le64 old_chunk; |
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__le64 new_chunk; |
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} __packed; |
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|
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struct core_exception { |
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uint64_t old_chunk; |
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uint64_t new_chunk; |
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}; |
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|
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struct commit_callback { |
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void (*callback)(void *, int success); |
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void *context; |
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}; |
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|
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/* |
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* The top level structure for a persistent exception store. |
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*/ |
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struct pstore { |
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struct dm_exception_store *store; |
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int version; |
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int valid; |
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uint32_t exceptions_per_area; |
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|
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/* |
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* Now that we have an asynchronous kcopyd there is no |
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* need for large chunk sizes, so it wont hurt to have a |
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* whole chunks worth of metadata in memory at once. |
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*/ |
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void *area; |
|
|
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/* |
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* An area of zeros used to clear the next area. |
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*/ |
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void *zero_area; |
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|
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/* |
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* An area used for header. The header can be written |
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* concurrently with metadata (when invalidating the snapshot), |
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* so it needs a separate buffer. |
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*/ |
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void *header_area; |
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|
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/* |
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* Used to keep track of which metadata area the data in |
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* 'chunk' refers to. |
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*/ |
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chunk_t current_area; |
|
|
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/* |
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* The next free chunk for an exception. |
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* |
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* When creating exceptions, all the chunks here and above are |
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* free. It holds the next chunk to be allocated. On rare |
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* occasions (e.g. after a system crash) holes can be left in |
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* the exception store because chunks can be committed out of |
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* order. |
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* |
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* When merging exceptions, it does not necessarily mean all the |
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* chunks here and above are free. It holds the value it would |
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* have held if all chunks had been committed in order of |
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* allocation. Consequently the value may occasionally be |
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* slightly too low, but since it's only used for 'status' and |
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* it can never reach its minimum value too early this doesn't |
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* matter. |
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*/ |
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|
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chunk_t next_free; |
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|
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/* |
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* The index of next free exception in the current |
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* metadata area. |
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*/ |
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uint32_t current_committed; |
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|
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atomic_t pending_count; |
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uint32_t callback_count; |
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struct commit_callback *callbacks; |
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struct dm_io_client *io_client; |
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|
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struct workqueue_struct *metadata_wq; |
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}; |
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|
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static int alloc_area(struct pstore *ps) |
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{ |
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int r = -ENOMEM; |
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size_t len; |
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|
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len = ps->store->chunk_size << SECTOR_SHIFT; |
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|
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/* |
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* Allocate the chunk_size block of memory that will hold |
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* a single metadata area. |
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*/ |
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ps->area = vmalloc(len); |
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if (!ps->area) |
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goto err_area; |
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|
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ps->zero_area = vzalloc(len); |
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if (!ps->zero_area) |
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goto err_zero_area; |
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|
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ps->header_area = vmalloc(len); |
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if (!ps->header_area) |
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goto err_header_area; |
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|
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return 0; |
|
|
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err_header_area: |
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vfree(ps->zero_area); |
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|
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err_zero_area: |
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vfree(ps->area); |
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|
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err_area: |
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return r; |
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} |
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|
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static void free_area(struct pstore *ps) |
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{ |
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vfree(ps->area); |
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ps->area = NULL; |
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vfree(ps->zero_area); |
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ps->zero_area = NULL; |
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vfree(ps->header_area); |
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ps->header_area = NULL; |
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} |
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|
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struct mdata_req { |
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struct dm_io_region *where; |
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struct dm_io_request *io_req; |
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struct work_struct work; |
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int result; |
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}; |
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|
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static void do_metadata(struct work_struct *work) |
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{ |
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struct mdata_req *req = container_of(work, struct mdata_req, work); |
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|
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req->result = dm_io(req->io_req, 1, req->where, NULL); |
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} |
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|
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/* |
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* Read or write a chunk aligned and sized block of data from a device. |
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*/ |
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static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int op, |
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int op_flags, int metadata) |
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{ |
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struct dm_io_region where = { |
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.bdev = dm_snap_cow(ps->store->snap)->bdev, |
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.sector = ps->store->chunk_size * chunk, |
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.count = ps->store->chunk_size, |
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}; |
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struct dm_io_request io_req = { |
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.bi_op = op, |
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.bi_op_flags = op_flags, |
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.mem.type = DM_IO_VMA, |
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.mem.ptr.vma = area, |
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.client = ps->io_client, |
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.notify.fn = NULL, |
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}; |
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struct mdata_req req; |
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|
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if (!metadata) |
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return dm_io(&io_req, 1, &where, NULL); |
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|
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req.where = &where; |
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req.io_req = &io_req; |
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|
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/* |
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* Issue the synchronous I/O from a different thread |
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* to avoid submit_bio_noacct recursion. |
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*/ |
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INIT_WORK_ONSTACK(&req.work, do_metadata); |
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queue_work(ps->metadata_wq, &req.work); |
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flush_workqueue(ps->metadata_wq); |
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destroy_work_on_stack(&req.work); |
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|
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return req.result; |
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} |
|
|
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/* |
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* Convert a metadata area index to a chunk index. |
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*/ |
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static chunk_t area_location(struct pstore *ps, chunk_t area) |
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{ |
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return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area); |
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} |
|
|
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static void skip_metadata(struct pstore *ps) |
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{ |
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uint32_t stride = ps->exceptions_per_area + 1; |
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chunk_t next_free = ps->next_free; |
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if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS) |
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ps->next_free++; |
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} |
|
|
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/* |
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* Read or write a metadata area. Remembering to skip the first |
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* chunk which holds the header. |
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*/ |
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static int area_io(struct pstore *ps, int op, int op_flags) |
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{ |
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chunk_t chunk = area_location(ps, ps->current_area); |
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|
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return chunk_io(ps, ps->area, chunk, op, op_flags, 0); |
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} |
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|
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static void zero_memory_area(struct pstore *ps) |
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{ |
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memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT); |
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} |
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|
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static int zero_disk_area(struct pstore *ps, chunk_t area) |
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{ |
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return chunk_io(ps, ps->zero_area, area_location(ps, area), |
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REQ_OP_WRITE, 0, 0); |
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} |
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|
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static int read_header(struct pstore *ps, int *new_snapshot) |
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{ |
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int r; |
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struct disk_header *dh; |
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unsigned chunk_size; |
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int chunk_size_supplied = 1; |
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char *chunk_err; |
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|
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/* |
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* Use default chunk size (or logical_block_size, if larger) |
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* if none supplied |
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*/ |
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if (!ps->store->chunk_size) { |
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ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS, |
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bdev_logical_block_size(dm_snap_cow(ps->store->snap)-> |
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bdev) >> 9); |
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ps->store->chunk_mask = ps->store->chunk_size - 1; |
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ps->store->chunk_shift = __ffs(ps->store->chunk_size); |
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chunk_size_supplied = 0; |
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} |
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|
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ps->io_client = dm_io_client_create(); |
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if (IS_ERR(ps->io_client)) |
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return PTR_ERR(ps->io_client); |
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|
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r = alloc_area(ps); |
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if (r) |
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return r; |
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|
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r = chunk_io(ps, ps->header_area, 0, REQ_OP_READ, 0, 1); |
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if (r) |
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goto bad; |
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dh = ps->header_area; |
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|
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if (le32_to_cpu(dh->magic) == 0) { |
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*new_snapshot = 1; |
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return 0; |
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} |
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|
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if (le32_to_cpu(dh->magic) != SNAP_MAGIC) { |
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DMWARN("Invalid or corrupt snapshot"); |
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r = -ENXIO; |
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goto bad; |
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} |
|
|
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*new_snapshot = 0; |
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ps->valid = le32_to_cpu(dh->valid); |
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ps->version = le32_to_cpu(dh->version); |
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chunk_size = le32_to_cpu(dh->chunk_size); |
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|
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if (ps->store->chunk_size == chunk_size) |
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return 0; |
|
|
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if (chunk_size_supplied) |
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DMWARN("chunk size %u in device metadata overrides " |
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"table chunk size of %u.", |
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chunk_size, ps->store->chunk_size); |
|
|
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/* We had a bogus chunk_size. Fix stuff up. */ |
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free_area(ps); |
|
|
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r = dm_exception_store_set_chunk_size(ps->store, chunk_size, |
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&chunk_err); |
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if (r) { |
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DMERR("invalid on-disk chunk size %u: %s.", |
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chunk_size, chunk_err); |
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return r; |
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} |
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|
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r = alloc_area(ps); |
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return r; |
|
|
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bad: |
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free_area(ps); |
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return r; |
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} |
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|
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static int write_header(struct pstore *ps) |
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{ |
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struct disk_header *dh; |
|
|
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memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT); |
|
|
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dh = ps->header_area; |
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dh->magic = cpu_to_le32(SNAP_MAGIC); |
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dh->valid = cpu_to_le32(ps->valid); |
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dh->version = cpu_to_le32(ps->version); |
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dh->chunk_size = cpu_to_le32(ps->store->chunk_size); |
|
|
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return chunk_io(ps, ps->header_area, 0, REQ_OP_WRITE, 0, 1); |
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} |
|
|
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/* |
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* Access functions for the disk exceptions, these do the endian conversions. |
|
*/ |
|
static struct disk_exception *get_exception(struct pstore *ps, void *ps_area, |
|
uint32_t index) |
|
{ |
|
BUG_ON(index >= ps->exceptions_per_area); |
|
|
|
return ((struct disk_exception *) ps_area) + index; |
|
} |
|
|
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static void read_exception(struct pstore *ps, void *ps_area, |
|
uint32_t index, struct core_exception *result) |
|
{ |
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struct disk_exception *de = get_exception(ps, ps_area, index); |
|
|
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/* copy it */ |
|
result->old_chunk = le64_to_cpu(de->old_chunk); |
|
result->new_chunk = le64_to_cpu(de->new_chunk); |
|
} |
|
|
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static void write_exception(struct pstore *ps, |
|
uint32_t index, struct core_exception *e) |
|
{ |
|
struct disk_exception *de = get_exception(ps, ps->area, index); |
|
|
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/* copy it */ |
|
de->old_chunk = cpu_to_le64(e->old_chunk); |
|
de->new_chunk = cpu_to_le64(e->new_chunk); |
|
} |
|
|
|
static void clear_exception(struct pstore *ps, uint32_t index) |
|
{ |
|
struct disk_exception *de = get_exception(ps, ps->area, index); |
|
|
|
/* clear it */ |
|
de->old_chunk = 0; |
|
de->new_chunk = 0; |
|
} |
|
|
|
/* |
|
* Registers the exceptions that are present in the current area. |
|
* 'full' is filled in to indicate if the area has been |
|
* filled. |
|
*/ |
|
static int insert_exceptions(struct pstore *ps, void *ps_area, |
|
int (*callback)(void *callback_context, |
|
chunk_t old, chunk_t new), |
|
void *callback_context, |
|
int *full) |
|
{ |
|
int r; |
|
unsigned int i; |
|
struct core_exception e; |
|
|
|
/* presume the area is full */ |
|
*full = 1; |
|
|
|
for (i = 0; i < ps->exceptions_per_area; i++) { |
|
read_exception(ps, ps_area, i, &e); |
|
|
|
/* |
|
* If the new_chunk is pointing at the start of |
|
* the COW device, where the first metadata area |
|
* is we know that we've hit the end of the |
|
* exceptions. Therefore the area is not full. |
|
*/ |
|
if (e.new_chunk == 0LL) { |
|
ps->current_committed = i; |
|
*full = 0; |
|
break; |
|
} |
|
|
|
/* |
|
* Keep track of the start of the free chunks. |
|
*/ |
|
if (ps->next_free <= e.new_chunk) |
|
ps->next_free = e.new_chunk + 1; |
|
|
|
/* |
|
* Otherwise we add the exception to the snapshot. |
|
*/ |
|
r = callback(callback_context, e.old_chunk, e.new_chunk); |
|
if (r) |
|
return r; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static int read_exceptions(struct pstore *ps, |
|
int (*callback)(void *callback_context, chunk_t old, |
|
chunk_t new), |
|
void *callback_context) |
|
{ |
|
int r, full = 1; |
|
struct dm_bufio_client *client; |
|
chunk_t prefetch_area = 0; |
|
|
|
client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev, |
|
ps->store->chunk_size << SECTOR_SHIFT, |
|
1, 0, NULL, NULL); |
|
|
|
if (IS_ERR(client)) |
|
return PTR_ERR(client); |
|
|
|
/* |
|
* Setup for one current buffer + desired readahead buffers. |
|
*/ |
|
dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS); |
|
|
|
/* |
|
* Keeping reading chunks and inserting exceptions until |
|
* we find a partially full area. |
|
*/ |
|
for (ps->current_area = 0; full; ps->current_area++) { |
|
struct dm_buffer *bp; |
|
void *area; |
|
chunk_t chunk; |
|
|
|
if (unlikely(prefetch_area < ps->current_area)) |
|
prefetch_area = ps->current_area; |
|
|
|
if (DM_PREFETCH_CHUNKS) do { |
|
chunk_t pf_chunk = area_location(ps, prefetch_area); |
|
if (unlikely(pf_chunk >= dm_bufio_get_device_size(client))) |
|
break; |
|
dm_bufio_prefetch(client, pf_chunk, 1); |
|
prefetch_area++; |
|
if (unlikely(!prefetch_area)) |
|
break; |
|
} while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS); |
|
|
|
chunk = area_location(ps, ps->current_area); |
|
|
|
area = dm_bufio_read(client, chunk, &bp); |
|
if (IS_ERR(area)) { |
|
r = PTR_ERR(area); |
|
goto ret_destroy_bufio; |
|
} |
|
|
|
r = insert_exceptions(ps, area, callback, callback_context, |
|
&full); |
|
|
|
if (!full) |
|
memcpy(ps->area, area, ps->store->chunk_size << SECTOR_SHIFT); |
|
|
|
dm_bufio_release(bp); |
|
|
|
dm_bufio_forget(client, chunk); |
|
|
|
if (unlikely(r)) |
|
goto ret_destroy_bufio; |
|
} |
|
|
|
ps->current_area--; |
|
|
|
skip_metadata(ps); |
|
|
|
r = 0; |
|
|
|
ret_destroy_bufio: |
|
dm_bufio_client_destroy(client); |
|
|
|
return r; |
|
} |
|
|
|
static struct pstore *get_info(struct dm_exception_store *store) |
|
{ |
|
return (struct pstore *) store->context; |
|
} |
|
|
|
static void persistent_usage(struct dm_exception_store *store, |
|
sector_t *total_sectors, |
|
sector_t *sectors_allocated, |
|
sector_t *metadata_sectors) |
|
{ |
|
struct pstore *ps = get_info(store); |
|
|
|
*sectors_allocated = ps->next_free * store->chunk_size; |
|
*total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev); |
|
|
|
/* |
|
* First chunk is the fixed header. |
|
* Then there are (ps->current_area + 1) metadata chunks, each one |
|
* separated from the next by ps->exceptions_per_area data chunks. |
|
*/ |
|
*metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) * |
|
store->chunk_size; |
|
} |
|
|
|
static void persistent_dtr(struct dm_exception_store *store) |
|
{ |
|
struct pstore *ps = get_info(store); |
|
|
|
destroy_workqueue(ps->metadata_wq); |
|
|
|
/* Created in read_header */ |
|
if (ps->io_client) |
|
dm_io_client_destroy(ps->io_client); |
|
free_area(ps); |
|
|
|
/* Allocated in persistent_read_metadata */ |
|
vfree(ps->callbacks); |
|
|
|
kfree(ps); |
|
} |
|
|
|
static int persistent_read_metadata(struct dm_exception_store *store, |
|
int (*callback)(void *callback_context, |
|
chunk_t old, chunk_t new), |
|
void *callback_context) |
|
{ |
|
int r, new_snapshot; |
|
struct pstore *ps = get_info(store); |
|
|
|
/* |
|
* Read the snapshot header. |
|
*/ |
|
r = read_header(ps, &new_snapshot); |
|
if (r) |
|
return r; |
|
|
|
/* |
|
* Now we know correct chunk_size, complete the initialisation. |
|
*/ |
|
ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) / |
|
sizeof(struct disk_exception); |
|
ps->callbacks = dm_vcalloc(ps->exceptions_per_area, |
|
sizeof(*ps->callbacks)); |
|
if (!ps->callbacks) |
|
return -ENOMEM; |
|
|
|
/* |
|
* Do we need to setup a new snapshot ? |
|
*/ |
|
if (new_snapshot) { |
|
r = write_header(ps); |
|
if (r) { |
|
DMWARN("write_header failed"); |
|
return r; |
|
} |
|
|
|
ps->current_area = 0; |
|
zero_memory_area(ps); |
|
r = zero_disk_area(ps, 0); |
|
if (r) |
|
DMWARN("zero_disk_area(0) failed"); |
|
return r; |
|
} |
|
/* |
|
* Sanity checks. |
|
*/ |
|
if (ps->version != SNAPSHOT_DISK_VERSION) { |
|
DMWARN("unable to handle snapshot disk version %d", |
|
ps->version); |
|
return -EINVAL; |
|
} |
|
|
|
/* |
|
* Metadata are valid, but snapshot is invalidated |
|
*/ |
|
if (!ps->valid) |
|
return 1; |
|
|
|
/* |
|
* Read the metadata. |
|
*/ |
|
r = read_exceptions(ps, callback, callback_context); |
|
|
|
return r; |
|
} |
|
|
|
static int persistent_prepare_exception(struct dm_exception_store *store, |
|
struct dm_exception *e) |
|
{ |
|
struct pstore *ps = get_info(store); |
|
sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev); |
|
|
|
/* Is there enough room ? */ |
|
if (size < ((ps->next_free + 1) * store->chunk_size)) |
|
return -ENOSPC; |
|
|
|
e->new_chunk = ps->next_free; |
|
|
|
/* |
|
* Move onto the next free pending, making sure to take |
|
* into account the location of the metadata chunks. |
|
*/ |
|
ps->next_free++; |
|
skip_metadata(ps); |
|
|
|
atomic_inc(&ps->pending_count); |
|
return 0; |
|
} |
|
|
|
static void persistent_commit_exception(struct dm_exception_store *store, |
|
struct dm_exception *e, int valid, |
|
void (*callback) (void *, int success), |
|
void *callback_context) |
|
{ |
|
unsigned int i; |
|
struct pstore *ps = get_info(store); |
|
struct core_exception ce; |
|
struct commit_callback *cb; |
|
|
|
if (!valid) |
|
ps->valid = 0; |
|
|
|
ce.old_chunk = e->old_chunk; |
|
ce.new_chunk = e->new_chunk; |
|
write_exception(ps, ps->current_committed++, &ce); |
|
|
|
/* |
|
* Add the callback to the back of the array. This code |
|
* is the only place where the callback array is |
|
* manipulated, and we know that it will never be called |
|
* multiple times concurrently. |
|
*/ |
|
cb = ps->callbacks + ps->callback_count++; |
|
cb->callback = callback; |
|
cb->context = callback_context; |
|
|
|
/* |
|
* If there are exceptions in flight and we have not yet |
|
* filled this metadata area there's nothing more to do. |
|
*/ |
|
if (!atomic_dec_and_test(&ps->pending_count) && |
|
(ps->current_committed != ps->exceptions_per_area)) |
|
return; |
|
|
|
/* |
|
* If we completely filled the current area, then wipe the next one. |
|
*/ |
|
if ((ps->current_committed == ps->exceptions_per_area) && |
|
zero_disk_area(ps, ps->current_area + 1)) |
|
ps->valid = 0; |
|
|
|
/* |
|
* Commit exceptions to disk. |
|
*/ |
|
if (ps->valid && area_io(ps, REQ_OP_WRITE, |
|
REQ_PREFLUSH | REQ_FUA | REQ_SYNC)) |
|
ps->valid = 0; |
|
|
|
/* |
|
* Advance to the next area if this one is full. |
|
*/ |
|
if (ps->current_committed == ps->exceptions_per_area) { |
|
ps->current_committed = 0; |
|
ps->current_area++; |
|
zero_memory_area(ps); |
|
} |
|
|
|
for (i = 0; i < ps->callback_count; i++) { |
|
cb = ps->callbacks + i; |
|
cb->callback(cb->context, ps->valid); |
|
} |
|
|
|
ps->callback_count = 0; |
|
} |
|
|
|
static int persistent_prepare_merge(struct dm_exception_store *store, |
|
chunk_t *last_old_chunk, |
|
chunk_t *last_new_chunk) |
|
{ |
|
struct pstore *ps = get_info(store); |
|
struct core_exception ce; |
|
int nr_consecutive; |
|
int r; |
|
|
|
/* |
|
* When current area is empty, move back to preceding area. |
|
*/ |
|
if (!ps->current_committed) { |
|
/* |
|
* Have we finished? |
|
*/ |
|
if (!ps->current_area) |
|
return 0; |
|
|
|
ps->current_area--; |
|
r = area_io(ps, REQ_OP_READ, 0); |
|
if (r < 0) |
|
return r; |
|
ps->current_committed = ps->exceptions_per_area; |
|
} |
|
|
|
read_exception(ps, ps->area, ps->current_committed - 1, &ce); |
|
*last_old_chunk = ce.old_chunk; |
|
*last_new_chunk = ce.new_chunk; |
|
|
|
/* |
|
* Find number of consecutive chunks within the current area, |
|
* working backwards. |
|
*/ |
|
for (nr_consecutive = 1; nr_consecutive < ps->current_committed; |
|
nr_consecutive++) { |
|
read_exception(ps, ps->area, |
|
ps->current_committed - 1 - nr_consecutive, &ce); |
|
if (ce.old_chunk != *last_old_chunk - nr_consecutive || |
|
ce.new_chunk != *last_new_chunk - nr_consecutive) |
|
break; |
|
} |
|
|
|
return nr_consecutive; |
|
} |
|
|
|
static int persistent_commit_merge(struct dm_exception_store *store, |
|
int nr_merged) |
|
{ |
|
int r, i; |
|
struct pstore *ps = get_info(store); |
|
|
|
BUG_ON(nr_merged > ps->current_committed); |
|
|
|
for (i = 0; i < nr_merged; i++) |
|
clear_exception(ps, ps->current_committed - 1 - i); |
|
|
|
r = area_io(ps, REQ_OP_WRITE, REQ_PREFLUSH | REQ_FUA); |
|
if (r < 0) |
|
return r; |
|
|
|
ps->current_committed -= nr_merged; |
|
|
|
/* |
|
* At this stage, only persistent_usage() uses ps->next_free, so |
|
* we make no attempt to keep ps->next_free strictly accurate |
|
* as exceptions may have been committed out-of-order originally. |
|
* Once a snapshot has become merging, we set it to the value it |
|
* would have held had all the exceptions been committed in order. |
|
* |
|
* ps->current_area does not get reduced by prepare_merge() until |
|
* after commit_merge() has removed the nr_merged previous exceptions. |
|
*/ |
|
ps->next_free = area_location(ps, ps->current_area) + |
|
ps->current_committed + 1; |
|
|
|
return 0; |
|
} |
|
|
|
static void persistent_drop_snapshot(struct dm_exception_store *store) |
|
{ |
|
struct pstore *ps = get_info(store); |
|
|
|
ps->valid = 0; |
|
if (write_header(ps)) |
|
DMWARN("write header failed"); |
|
} |
|
|
|
static int persistent_ctr(struct dm_exception_store *store, char *options) |
|
{ |
|
struct pstore *ps; |
|
int r; |
|
|
|
/* allocate the pstore */ |
|
ps = kzalloc(sizeof(*ps), GFP_KERNEL); |
|
if (!ps) |
|
return -ENOMEM; |
|
|
|
ps->store = store; |
|
ps->valid = 1; |
|
ps->version = SNAPSHOT_DISK_VERSION; |
|
ps->area = NULL; |
|
ps->zero_area = NULL; |
|
ps->header_area = NULL; |
|
ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */ |
|
ps->current_committed = 0; |
|
|
|
ps->callback_count = 0; |
|
atomic_set(&ps->pending_count, 0); |
|
ps->callbacks = NULL; |
|
|
|
ps->metadata_wq = alloc_workqueue("ksnaphd", WQ_MEM_RECLAIM, 0); |
|
if (!ps->metadata_wq) { |
|
DMERR("couldn't start header metadata update thread"); |
|
r = -ENOMEM; |
|
goto err_workqueue; |
|
} |
|
|
|
if (options) { |
|
char overflow = toupper(options[0]); |
|
if (overflow == 'O') |
|
store->userspace_supports_overflow = true; |
|
else { |
|
DMERR("Unsupported persistent store option: %s", options); |
|
r = -EINVAL; |
|
goto err_options; |
|
} |
|
} |
|
|
|
store->context = ps; |
|
|
|
return 0; |
|
|
|
err_options: |
|
destroy_workqueue(ps->metadata_wq); |
|
err_workqueue: |
|
kfree(ps); |
|
|
|
return r; |
|
} |
|
|
|
static unsigned persistent_status(struct dm_exception_store *store, |
|
status_type_t status, char *result, |
|
unsigned maxlen) |
|
{ |
|
unsigned sz = 0; |
|
|
|
switch (status) { |
|
case STATUSTYPE_INFO: |
|
break; |
|
case STATUSTYPE_TABLE: |
|
DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P", |
|
(unsigned long long)store->chunk_size); |
|
} |
|
|
|
return sz; |
|
} |
|
|
|
static struct dm_exception_store_type _persistent_type = { |
|
.name = "persistent", |
|
.module = THIS_MODULE, |
|
.ctr = persistent_ctr, |
|
.dtr = persistent_dtr, |
|
.read_metadata = persistent_read_metadata, |
|
.prepare_exception = persistent_prepare_exception, |
|
.commit_exception = persistent_commit_exception, |
|
.prepare_merge = persistent_prepare_merge, |
|
.commit_merge = persistent_commit_merge, |
|
.drop_snapshot = persistent_drop_snapshot, |
|
.usage = persistent_usage, |
|
.status = persistent_status, |
|
}; |
|
|
|
static struct dm_exception_store_type _persistent_compat_type = { |
|
.name = "P", |
|
.module = THIS_MODULE, |
|
.ctr = persistent_ctr, |
|
.dtr = persistent_dtr, |
|
.read_metadata = persistent_read_metadata, |
|
.prepare_exception = persistent_prepare_exception, |
|
.commit_exception = persistent_commit_exception, |
|
.prepare_merge = persistent_prepare_merge, |
|
.commit_merge = persistent_commit_merge, |
|
.drop_snapshot = persistent_drop_snapshot, |
|
.usage = persistent_usage, |
|
.status = persistent_status, |
|
}; |
|
|
|
int dm_persistent_snapshot_init(void) |
|
{ |
|
int r; |
|
|
|
r = dm_exception_store_type_register(&_persistent_type); |
|
if (r) { |
|
DMERR("Unable to register persistent exception store type"); |
|
return r; |
|
} |
|
|
|
r = dm_exception_store_type_register(&_persistent_compat_type); |
|
if (r) { |
|
DMERR("Unable to register old-style persistent exception " |
|
"store type"); |
|
dm_exception_store_type_unregister(&_persistent_type); |
|
return r; |
|
} |
|
|
|
return r; |
|
} |
|
|
|
void dm_persistent_snapshot_exit(void) |
|
{ |
|
dm_exception_store_type_unregister(&_persistent_type); |
|
dm_exception_store_type_unregister(&_persistent_compat_type); |
|
}
|
|
|