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553 lines
18 KiB
553 lines
18 KiB
/* General filesystem caching backing cache interface |
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* |
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* Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. |
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* Written by David Howells ([email protected]) |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU General Public License |
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* as published by the Free Software Foundation; either version |
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* 2 of the License, or (at your option) any later version. |
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* |
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* NOTE!!! See: |
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* |
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* Documentation/filesystems/caching/backend-api.txt |
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* |
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* for a description of the cache backend interface declared here. |
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*/ |
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#ifndef _LINUX_FSCACHE_CACHE_H |
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#define _LINUX_FSCACHE_CACHE_H |
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#include <linux/fscache.h> |
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#include <linux/sched.h> |
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#include <linux/workqueue.h> |
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#define NR_MAXCACHES BITS_PER_LONG |
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struct fscache_cache; |
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struct fscache_cache_ops; |
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struct fscache_object; |
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struct fscache_operation; |
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/* |
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* cache tag definition |
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*/ |
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struct fscache_cache_tag { |
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struct list_head link; |
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struct fscache_cache *cache; /* cache referred to by this tag */ |
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unsigned long flags; |
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#define FSCACHE_TAG_RESERVED 0 /* T if tag is reserved for a cache */ |
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atomic_t usage; |
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char name[0]; /* tag name */ |
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}; |
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/* |
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* cache definition |
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*/ |
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struct fscache_cache { |
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const struct fscache_cache_ops *ops; |
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struct fscache_cache_tag *tag; /* tag representing this cache */ |
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struct kobject *kobj; /* system representation of this cache */ |
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struct list_head link; /* link in list of caches */ |
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size_t max_index_size; /* maximum size of index data */ |
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char identifier[36]; /* cache label */ |
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/* node management */ |
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struct work_struct op_gc; /* operation garbage collector */ |
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struct list_head object_list; /* list of data/index objects */ |
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struct list_head op_gc_list; /* list of ops to be deleted */ |
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spinlock_t object_list_lock; |
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spinlock_t op_gc_list_lock; |
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atomic_t object_count; /* no. of live objects in this cache */ |
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struct fscache_object *fsdef; /* object for the fsdef index */ |
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unsigned long flags; |
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#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */ |
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#define FSCACHE_CACHE_WITHDRAWN 1 /* cache has been withdrawn */ |
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}; |
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extern wait_queue_head_t fscache_cache_cleared_wq; |
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/* |
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* operation to be applied to a cache object |
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* - retrieval initiation operations are done in the context of the process |
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* that issued them, and not in an async thread pool |
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*/ |
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typedef void (*fscache_operation_release_t)(struct fscache_operation *op); |
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typedef void (*fscache_operation_processor_t)(struct fscache_operation *op); |
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typedef void (*fscache_operation_cancel_t)(struct fscache_operation *op); |
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enum fscache_operation_state { |
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FSCACHE_OP_ST_BLANK, /* Op is not yet submitted */ |
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FSCACHE_OP_ST_INITIALISED, /* Op is initialised */ |
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FSCACHE_OP_ST_PENDING, /* Op is blocked from running */ |
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FSCACHE_OP_ST_IN_PROGRESS, /* Op is in progress */ |
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FSCACHE_OP_ST_COMPLETE, /* Op is complete */ |
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FSCACHE_OP_ST_CANCELLED, /* Op has been cancelled */ |
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FSCACHE_OP_ST_DEAD /* Op is now dead */ |
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}; |
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struct fscache_operation { |
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struct work_struct work; /* record for async ops */ |
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struct list_head pend_link; /* link in object->pending_ops */ |
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struct fscache_object *object; /* object to be operated upon */ |
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unsigned long flags; |
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#define FSCACHE_OP_TYPE 0x000f /* operation type */ |
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#define FSCACHE_OP_ASYNC 0x0001 /* - async op, processor may sleep for disk */ |
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#define FSCACHE_OP_MYTHREAD 0x0002 /* - processing is done be issuing thread, not pool */ |
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#define FSCACHE_OP_WAITING 4 /* cleared when op is woken */ |
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#define FSCACHE_OP_EXCLUSIVE 5 /* exclusive op, other ops must wait */ |
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#define FSCACHE_OP_DEC_READ_CNT 6 /* decrement object->n_reads on destruction */ |
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#define FSCACHE_OP_UNUSE_COOKIE 7 /* call fscache_unuse_cookie() on completion */ |
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#define FSCACHE_OP_KEEP_FLAGS 0x00f0 /* flags to keep when repurposing an op */ |
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enum fscache_operation_state state; |
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atomic_t usage; |
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unsigned debug_id; /* debugging ID */ |
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/* operation processor callback |
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* - can be NULL if FSCACHE_OP_WAITING is going to be used to perform |
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* the op in a non-pool thread */ |
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fscache_operation_processor_t processor; |
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/* Operation cancellation cleanup (optional) */ |
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fscache_operation_cancel_t cancel; |
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/* operation releaser */ |
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fscache_operation_release_t release; |
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}; |
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extern atomic_unchecked_t fscache_op_debug_id; |
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extern void fscache_op_work_func(struct work_struct *work); |
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extern void fscache_enqueue_operation(struct fscache_operation *); |
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extern void fscache_op_complete(struct fscache_operation *, bool); |
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extern void fscache_put_operation(struct fscache_operation *); |
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extern void fscache_operation_init(struct fscache_operation *, |
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fscache_operation_processor_t, |
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fscache_operation_cancel_t, |
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fscache_operation_release_t); |
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/* |
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* data read operation |
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*/ |
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struct fscache_retrieval { |
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struct fscache_operation op; |
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struct fscache_cookie *cookie; /* The netfs cookie */ |
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struct address_space *mapping; /* netfs pages */ |
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fscache_rw_complete_t end_io_func; /* function to call on I/O completion */ |
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void *context; /* netfs read context (pinned) */ |
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struct list_head to_do; /* list of things to be done by the backend */ |
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unsigned long start_time; /* time at which retrieval started */ |
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atomic_t n_pages; /* number of pages to be retrieved */ |
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}; |
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typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op, |
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struct page *page, |
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gfp_t gfp); |
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typedef int (*fscache_pages_retrieval_func_t)(struct fscache_retrieval *op, |
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struct list_head *pages, |
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unsigned *nr_pages, |
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gfp_t gfp); |
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/** |
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* fscache_get_retrieval - Get an extra reference on a retrieval operation |
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* @op: The retrieval operation to get a reference on |
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* |
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* Get an extra reference on a retrieval operation. |
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*/ |
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static inline |
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struct fscache_retrieval *fscache_get_retrieval(struct fscache_retrieval *op) |
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{ |
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atomic_inc(&op->op.usage); |
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return op; |
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} |
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/** |
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* fscache_enqueue_retrieval - Enqueue a retrieval operation for processing |
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* @op: The retrieval operation affected |
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* |
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* Enqueue a retrieval operation for processing by the FS-Cache thread pool. |
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*/ |
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static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op) |
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{ |
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fscache_enqueue_operation(&op->op); |
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} |
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/** |
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* fscache_retrieval_complete - Record (partial) completion of a retrieval |
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* @op: The retrieval operation affected |
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* @n_pages: The number of pages to account for |
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*/ |
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static inline void fscache_retrieval_complete(struct fscache_retrieval *op, |
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int n_pages) |
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{ |
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atomic_sub(n_pages, &op->n_pages); |
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if (atomic_read(&op->n_pages) <= 0) |
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fscache_op_complete(&op->op, true); |
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} |
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/** |
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* fscache_put_retrieval - Drop a reference to a retrieval operation |
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* @op: The retrieval operation affected |
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* |
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* Drop a reference to a retrieval operation. |
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*/ |
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static inline void fscache_put_retrieval(struct fscache_retrieval *op) |
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{ |
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fscache_put_operation(&op->op); |
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} |
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/* |
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* cached page storage work item |
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* - used to do three things: |
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* - batch writes to the cache |
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* - do cache writes asynchronously |
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* - defer writes until cache object lookup completion |
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*/ |
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struct fscache_storage { |
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struct fscache_operation op; |
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pgoff_t store_limit; /* don't write more than this */ |
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}; |
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/* |
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* cache operations |
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*/ |
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struct fscache_cache_ops { |
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/* name of cache provider */ |
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const char *name; |
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/* allocate an object record for a cookie */ |
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struct fscache_object *(*alloc_object)(struct fscache_cache *cache, |
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struct fscache_cookie *cookie); |
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/* look up the object for a cookie |
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* - return -ETIMEDOUT to be requeued |
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*/ |
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int (*lookup_object)(struct fscache_object *object); |
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/* finished looking up */ |
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void (*lookup_complete)(struct fscache_object *object); |
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/* increment the usage count on this object (may fail if unmounting) */ |
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struct fscache_object *(*grab_object)(struct fscache_object *object); |
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/* pin an object in the cache */ |
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int (*pin_object)(struct fscache_object *object); |
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/* unpin an object in the cache */ |
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void (*unpin_object)(struct fscache_object *object); |
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/* check the consistency between the backing cache and the FS-Cache |
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* cookie */ |
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int (*check_consistency)(struct fscache_operation *op); |
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/* store the updated auxiliary data on an object */ |
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void (*update_object)(struct fscache_object *object); |
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/* Invalidate an object */ |
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void (*invalidate_object)(struct fscache_operation *op); |
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/* discard the resources pinned by an object and effect retirement if |
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* necessary */ |
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void (*drop_object)(struct fscache_object *object); |
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/* dispose of a reference to an object */ |
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void (*put_object)(struct fscache_object *object); |
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/* sync a cache */ |
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void (*sync_cache)(struct fscache_cache *cache); |
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/* notification that the attributes of a non-index object (such as |
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* i_size) have changed */ |
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int (*attr_changed)(struct fscache_object *object); |
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/* reserve space for an object's data and associated metadata */ |
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int (*reserve_space)(struct fscache_object *object, loff_t i_size); |
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/* request a backing block for a page be read or allocated in the |
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* cache */ |
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fscache_page_retrieval_func_t read_or_alloc_page; |
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/* request backing blocks for a list of pages be read or allocated in |
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* the cache */ |
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fscache_pages_retrieval_func_t read_or_alloc_pages; |
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/* request a backing block for a page be allocated in the cache so that |
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* it can be written directly */ |
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fscache_page_retrieval_func_t allocate_page; |
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/* request backing blocks for pages be allocated in the cache so that |
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* they can be written directly */ |
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fscache_pages_retrieval_func_t allocate_pages; |
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/* write a page to its backing block in the cache */ |
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int (*write_page)(struct fscache_storage *op, struct page *page); |
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/* detach backing block from a page (optional) |
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* - must release the cookie lock before returning |
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* - may sleep |
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*/ |
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void (*uncache_page)(struct fscache_object *object, |
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struct page *page); |
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/* dissociate a cache from all the pages it was backing */ |
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void (*dissociate_pages)(struct fscache_cache *cache); |
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}; |
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extern struct fscache_cookie fscache_fsdef_index; |
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/* |
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* Event list for fscache_object::{event_mask,events} |
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*/ |
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enum { |
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FSCACHE_OBJECT_EV_NEW_CHILD, /* T if object has a new child */ |
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FSCACHE_OBJECT_EV_PARENT_READY, /* T if object's parent is ready */ |
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FSCACHE_OBJECT_EV_UPDATE, /* T if object should be updated */ |
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FSCACHE_OBJECT_EV_INVALIDATE, /* T if cache requested object invalidation */ |
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FSCACHE_OBJECT_EV_CLEARED, /* T if accessors all gone */ |
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FSCACHE_OBJECT_EV_ERROR, /* T if fatal error occurred during processing */ |
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FSCACHE_OBJECT_EV_KILL, /* T if netfs relinquished or cache withdrew object */ |
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NR_FSCACHE_OBJECT_EVENTS |
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}; |
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#define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1) |
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/* |
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* States for object state machine. |
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*/ |
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struct fscache_transition { |
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unsigned long events; |
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const struct fscache_state *transit_to; |
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}; |
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struct fscache_state { |
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char name[24]; |
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char short_name[8]; |
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const struct fscache_state *(*work)(struct fscache_object *object, |
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int event); |
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const struct fscache_transition transitions[]; |
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}; |
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/* |
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* on-disk cache file or index handle |
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*/ |
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struct fscache_object { |
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const struct fscache_state *state; /* Object state machine state */ |
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const struct fscache_transition *oob_table; /* OOB state transition table */ |
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int debug_id; /* debugging ID */ |
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int n_children; /* number of child objects */ |
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int n_ops; /* number of extant ops on object */ |
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int n_obj_ops; /* number of object ops outstanding on object */ |
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int n_in_progress; /* number of ops in progress */ |
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int n_exclusive; /* number of exclusive ops queued or in progress */ |
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atomic_t n_reads; /* number of read ops in progress */ |
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spinlock_t lock; /* state and operations lock */ |
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unsigned long lookup_jif; /* time at which lookup started */ |
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unsigned long oob_event_mask; /* OOB events this object is interested in */ |
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unsigned long event_mask; /* events this object is interested in */ |
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unsigned long events; /* events to be processed by this object |
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* (order is important - using fls) */ |
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unsigned long flags; |
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#define FSCACHE_OBJECT_LOCK 0 /* T if object is busy being processed */ |
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#define FSCACHE_OBJECT_PENDING_WRITE 1 /* T if object has pending write */ |
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#define FSCACHE_OBJECT_WAITING 2 /* T if object is waiting on its parent */ |
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#define FSCACHE_OBJECT_IS_LIVE 3 /* T if object is not withdrawn or relinquished */ |
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#define FSCACHE_OBJECT_IS_LOOKED_UP 4 /* T if object has been looked up */ |
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#define FSCACHE_OBJECT_IS_AVAILABLE 5 /* T if object has become active */ |
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#define FSCACHE_OBJECT_RETIRED 6 /* T if object was retired on relinquishment */ |
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#define FSCACHE_OBJECT_KILLED_BY_CACHE 7 /* T if object was killed by the cache */ |
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struct list_head cache_link; /* link in cache->object_list */ |
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struct hlist_node cookie_link; /* link in cookie->backing_objects */ |
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struct fscache_cache *cache; /* cache that supplied this object */ |
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struct fscache_cookie *cookie; /* netfs's file/index object */ |
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struct fscache_object *parent; /* parent object */ |
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struct work_struct work; /* attention scheduling record */ |
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struct list_head dependents; /* FIFO of dependent objects */ |
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struct list_head dep_link; /* link in parent's dependents list */ |
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struct list_head pending_ops; /* unstarted operations on this object */ |
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#ifdef CONFIG_FSCACHE_OBJECT_LIST |
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struct rb_node objlist_link; /* link in global object list */ |
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#endif |
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pgoff_t store_limit; /* current storage limit */ |
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loff_t store_limit_l; /* current storage limit */ |
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}; |
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extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *, |
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struct fscache_cache *); |
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extern void fscache_object_destroy(struct fscache_object *); |
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extern void fscache_object_lookup_negative(struct fscache_object *object); |
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extern void fscache_obtained_object(struct fscache_object *object); |
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static inline bool fscache_object_is_live(struct fscache_object *object) |
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{ |
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return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags); |
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} |
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static inline bool fscache_object_is_dying(struct fscache_object *object) |
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{ |
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return !fscache_object_is_live(object); |
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} |
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static inline bool fscache_object_is_available(struct fscache_object *object) |
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{ |
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return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags); |
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} |
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static inline bool fscache_cache_is_broken(struct fscache_object *object) |
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{ |
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return test_bit(FSCACHE_IOERROR, &object->cache->flags); |
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} |
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static inline bool fscache_object_is_active(struct fscache_object *object) |
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{ |
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return fscache_object_is_available(object) && |
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fscache_object_is_live(object) && |
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!fscache_cache_is_broken(object); |
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} |
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/** |
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* fscache_object_destroyed - Note destruction of an object in a cache |
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* @cache: The cache from which the object came |
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* |
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* Note the destruction and deallocation of an object record in a cache. |
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*/ |
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static inline void fscache_object_destroyed(struct fscache_cache *cache) |
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{ |
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if (atomic_dec_and_test(&cache->object_count)) |
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wake_up_all(&fscache_cache_cleared_wq); |
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} |
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/** |
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* fscache_object_lookup_error - Note an object encountered an error |
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* @object: The object on which the error was encountered |
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* |
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* Note that an object encountered a fatal error (usually an I/O error) and |
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* that it should be withdrawn as soon as possible. |
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*/ |
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static inline void fscache_object_lookup_error(struct fscache_object *object) |
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{ |
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set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events); |
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} |
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/** |
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* fscache_set_store_limit - Set the maximum size to be stored in an object |
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* @object: The object to set the maximum on |
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* @i_size: The limit to set in bytes |
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* |
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* Set the maximum size an object is permitted to reach, implying the highest |
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* byte that may be written. Intended to be called by the attr_changed() op. |
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* |
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* See Documentation/filesystems/caching/backend-api.txt for a complete |
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* description. |
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*/ |
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static inline |
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void fscache_set_store_limit(struct fscache_object *object, loff_t i_size) |
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{ |
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object->store_limit_l = i_size; |
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object->store_limit = i_size >> PAGE_SHIFT; |
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if (i_size & ~PAGE_MASK) |
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object->store_limit++; |
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} |
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/** |
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* fscache_end_io - End a retrieval operation on a page |
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* @op: The FS-Cache operation covering the retrieval |
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* @page: The page that was to be fetched |
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* @error: The error code (0 if successful) |
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* |
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* Note the end of an operation to retrieve a page, as covered by a particular |
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* operation record. |
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*/ |
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static inline void fscache_end_io(struct fscache_retrieval *op, |
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struct page *page, int error) |
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{ |
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op->end_io_func(page, op->context, error); |
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} |
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static inline void __fscache_use_cookie(struct fscache_cookie *cookie) |
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{ |
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atomic_inc(&cookie->n_active); |
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} |
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/** |
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* fscache_use_cookie - Request usage of cookie attached to an object |
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* @object: Object description |
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* |
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* Request usage of the cookie attached to an object. NULL is returned if the |
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* relinquishment had reduced the cookie usage count to 0. |
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*/ |
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static inline bool fscache_use_cookie(struct fscache_object *object) |
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{ |
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struct fscache_cookie *cookie = object->cookie; |
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return atomic_inc_not_zero(&cookie->n_active) != 0; |
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} |
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static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie) |
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{ |
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return atomic_dec_and_test(&cookie->n_active); |
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} |
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static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie) |
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{ |
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wake_up_atomic_t(&cookie->n_active); |
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} |
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/** |
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* fscache_unuse_cookie - Cease usage of cookie attached to an object |
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* @object: Object description |
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* |
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* Cease usage of the cookie attached to an object. When the users count |
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* reaches zero then the cookie relinquishment will be permitted to proceed. |
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*/ |
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static inline void fscache_unuse_cookie(struct fscache_object *object) |
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{ |
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struct fscache_cookie *cookie = object->cookie; |
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if (__fscache_unuse_cookie(cookie)) |
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__fscache_wake_unused_cookie(cookie); |
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} |
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/* |
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* out-of-line cache backend functions |
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*/ |
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extern __printf(3, 4) |
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void fscache_init_cache(struct fscache_cache *cache, |
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const struct fscache_cache_ops *ops, |
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const char *idfmt, ...); |
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extern int fscache_add_cache(struct fscache_cache *cache, |
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struct fscache_object *fsdef, |
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const char *tagname); |
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extern void fscache_withdraw_cache(struct fscache_cache *cache); |
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extern void fscache_io_error(struct fscache_cache *cache); |
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extern void fscache_mark_page_cached(struct fscache_retrieval *op, |
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struct page *page); |
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extern void fscache_mark_pages_cached(struct fscache_retrieval *op, |
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struct pagevec *pagevec); |
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extern bool fscache_object_sleep_till_congested(signed long *timeoutp); |
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extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object, |
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const void *data, |
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uint16_t datalen); |
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extern void fscache_object_retrying_stale(struct fscache_object *object); |
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enum fscache_why_object_killed { |
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FSCACHE_OBJECT_IS_STALE, |
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FSCACHE_OBJECT_NO_SPACE, |
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FSCACHE_OBJECT_WAS_RETIRED, |
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FSCACHE_OBJECT_WAS_CULLED, |
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}; |
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extern void fscache_object_mark_killed(struct fscache_object *object, |
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enum fscache_why_object_killed why); |
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#endif /* _LINUX_FSCACHE_CACHE_H */
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