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FS-Cache: Add the FS-Cache cache backend API and documentation
Add the API for a generic facility (FS-Cache) by which caches may declare them selves open for business, and may obtain work to be done from network filesystems. The header file is included by: #include <linux/fscache-cache.h> Documentation for the API is also added to: Documentation/filesystems/caching/backend-api.txt This API is not usable without the implementation of the utility functions which will be added in further patches. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
This commit is contained in:
David Howells
parent
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2 changed files with 1173 additions and 0 deletions
509
include/linux/fscache-cache.h
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509
include/linux/fscache-cache.h
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/* 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 (dhowells@redhat.com)
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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/slow-work.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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#ifdef CONFIG_FSCACHE_PROC
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extern struct proc_dir_entry *proc_fscache;
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#endif
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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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struct fscache_operation {
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union {
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struct work_struct fast_work; /* record for fast ops */
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struct slow_work slow_work; /* record for (very) slow ops */
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};
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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_FAST 0x0001 /* - fast op, processor may not sleep for disk */
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#define FSCACHE_OP_SLOW 0x0002 /* - (very) slow op, processor may sleep for disk */
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#define FSCACHE_OP_MYTHREAD 0x0003 /* - 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_DEAD 6 /* op is now dead */
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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 releaser */
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fscache_operation_release_t release;
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};
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extern atomic_t fscache_op_debug_id;
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extern const struct slow_work_ops fscache_op_slow_work_ops;
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extern void fscache_enqueue_operation(struct fscache_operation *);
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extern void fscache_put_operation(struct fscache_operation *);
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/**
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* fscache_operation_init - Do basic initialisation of an operation
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* @op: The operation to initialise
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* @release: The release function to assign
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*
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* Do basic initialisation of an operation. The caller must still set flags,
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* object, either fast_work or slow_work if necessary, and processor if needed.
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*/
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static inline void fscache_operation_init(struct fscache_operation *op,
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fscache_operation_release_t release)
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{
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atomic_set(&op->usage, 1);
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op->debug_id = atomic_inc_return(&fscache_op_debug_id);
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op->release = release;
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INIT_LIST_HEAD(&op->pend_link);
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}
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/**
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* fscache_operation_init_slow - Do additional initialisation of a slow op
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* @op: The operation to initialise
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* @processor: The processor function to assign
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*
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* Do additional initialisation of an operation as required for slow work.
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*/
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static inline
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void fscache_operation_init_slow(struct fscache_operation *op,
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fscache_operation_processor_t processor)
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{
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op->processor = processor;
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slow_work_init(&op->slow_work, &fscache_op_slow_work_ops);
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}
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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 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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};
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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_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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void (*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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/* store the updated auxilliary data on an object */
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void (*update_object)(struct fscache_object *object);
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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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/*
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* data file or index object cookie
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* - a file will only appear in one cache
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* - a request to cache a file may or may not be honoured, subject to
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* constraints such as disk space
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* - indices are created on disk just-in-time
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*/
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struct fscache_cookie {
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atomic_t usage; /* number of users of this cookie */
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atomic_t n_children; /* number of children of this cookie */
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spinlock_t lock;
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struct hlist_head backing_objects; /* object(s) backing this file/index */
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const struct fscache_cookie_def *def; /* definition */
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struct fscache_cookie *parent; /* parent of this entry */
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void *netfs_data; /* back pointer to netfs */
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struct radix_tree_root stores; /* pages to be stored on this cookie */
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#define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
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unsigned long flags;
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#define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
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#define FSCACHE_COOKIE_CREATING 1 /* T if non-index object being created still */
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#define FSCACHE_COOKIE_NO_DATA_YET 2 /* T if new object with no cached data yet */
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#define FSCACHE_COOKIE_PENDING_FILL 3 /* T if pending initial fill on object */
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#define FSCACHE_COOKIE_FILLING 4 /* T if filling object incrementally */
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#define FSCACHE_COOKIE_UNAVAILABLE 5 /* T if cookie is unavailable (error, etc) */
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};
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extern struct fscache_cookie fscache_fsdef_index;
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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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enum fscache_object_state {
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FSCACHE_OBJECT_INIT, /* object in initial unbound state */
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FSCACHE_OBJECT_LOOKING_UP, /* looking up object */
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FSCACHE_OBJECT_CREATING, /* creating object */
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/* active states */
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FSCACHE_OBJECT_AVAILABLE, /* cleaning up object after creation */
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FSCACHE_OBJECT_ACTIVE, /* object is usable */
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FSCACHE_OBJECT_UPDATING, /* object is updating */
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/* terminal states */
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FSCACHE_OBJECT_DYING, /* object waiting for accessors to finish */
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FSCACHE_OBJECT_LC_DYING, /* object cleaning up after lookup/create */
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FSCACHE_OBJECT_ABORT_INIT, /* abort the init state */
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FSCACHE_OBJECT_RELEASING, /* releasing object */
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FSCACHE_OBJECT_RECYCLING, /* retiring object */
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FSCACHE_OBJECT_WITHDRAWING, /* withdrawing object */
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FSCACHE_OBJECT_DEAD, /* object is now dead */
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} state;
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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 ops outstanding 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 */
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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 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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#define FSCACHE_OBJECT_EV_REQUEUE 0 /* T if object should be requeued */
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#define FSCACHE_OBJECT_EV_UPDATE 1 /* T if object should be updated */
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#define FSCACHE_OBJECT_EV_CLEARED 2 /* T if accessors all gone */
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#define FSCACHE_OBJECT_EV_ERROR 3 /* T if fatal error occurred during processing */
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#define FSCACHE_OBJECT_EV_RELEASE 4 /* T if netfs requested object release */
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#define FSCACHE_OBJECT_EV_RETIRE 5 /* T if netfs requested object retirement */
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#define FSCACHE_OBJECT_EV_WITHDRAW 6 /* T if cache requested object withdrawal */
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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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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 slow_work 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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pgoff_t store_limit; /* current storage limit */
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};
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extern const char *fscache_object_states[];
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#define fscache_object_is_active(obj) \
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(!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) && \
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(obj)->state >= FSCACHE_OBJECT_AVAILABLE && \
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(obj)->state < FSCACHE_OBJECT_DYING)
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extern const struct slow_work_ops fscache_object_slow_work_ops;
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/**
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* fscache_object_init - Initialise a cache object description
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* @object: Object description
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*
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* Initialise a cache object description to its basic values.
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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_object_init(struct fscache_object *object,
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struct fscache_cookie *cookie,
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struct fscache_cache *cache)
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{
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atomic_inc(&cache->object_count);
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object->state = FSCACHE_OBJECT_INIT;
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spin_lock_init(&object->lock);
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INIT_LIST_HEAD(&object->cache_link);
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INIT_HLIST_NODE(&object->cookie_link);
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vslow_work_init(&object->work, &fscache_object_slow_work_ops);
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INIT_LIST_HEAD(&object->dependents);
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INIT_LIST_HEAD(&object->dep_link);
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INIT_LIST_HEAD(&object->pending_ops);
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object->n_children = 0;
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object->n_ops = object->n_in_progress = object->n_exclusive = 0;
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object->events = object->event_mask = 0;
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object->flags = 0;
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object->store_limit = 0;
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object->cache = cache;
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object->cookie = cookie;
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object->parent = NULL;
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}
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extern void fscache_object_lookup_negative(struct fscache_object *object);
|
||||
extern void fscache_obtained_object(struct fscache_object *object);
|
||||
|
||||
/**
|
||||
* fscache_object_destroyed - Note destruction of an object in a cache
|
||||
* @cache: The cache from which the object came
|
||||
*
|
||||
* Note the destruction and deallocation of an object record in a cache.
|
||||
*/
|
||||
static inline void fscache_object_destroyed(struct fscache_cache *cache)
|
||||
{
|
||||
if (atomic_dec_and_test(&cache->object_count))
|
||||
wake_up_all(&fscache_cache_cleared_wq);
|
||||
}
|
||||
|
||||
/**
|
||||
* fscache_object_lookup_error - Note an object encountered an error
|
||||
* @object: The object on which the error was encountered
|
||||
*
|
||||
* Note that an object encountered a fatal error (usually an I/O error) and
|
||||
* that it should be withdrawn as soon as possible.
|
||||
*/
|
||||
static inline void fscache_object_lookup_error(struct fscache_object *object)
|
||||
{
|
||||
set_bit(FSCACHE_OBJECT_EV_ERROR, &object->events);
|
||||
}
|
||||
|
||||
/**
|
||||
* fscache_set_store_limit - Set the maximum size to be stored in an object
|
||||
* @object: The object to set the maximum on
|
||||
* @i_size: The limit to set in bytes
|
||||
*
|
||||
* Set the maximum size an object is permitted to reach, implying the highest
|
||||
* byte that may be written. Intended to be called by the attr_changed() op.
|
||||
*
|
||||
* See Documentation/filesystems/caching/backend-api.txt for a complete
|
||||
* description.
|
||||
*/
|
||||
static inline
|
||||
void fscache_set_store_limit(struct fscache_object *object, loff_t i_size)
|
||||
{
|
||||
object->store_limit = i_size >> PAGE_SHIFT;
|
||||
if (i_size & ~PAGE_MASK)
|
||||
object->store_limit++;
|
||||
}
|
||||
|
||||
/**
|
||||
* fscache_end_io - End a retrieval operation on a page
|
||||
* @op: The FS-Cache operation covering the retrieval
|
||||
* @page: The page that was to be fetched
|
||||
* @error: The error code (0 if successful)
|
||||
*
|
||||
* Note the end of an operation to retrieve a page, as covered by a particular
|
||||
* operation record.
|
||||
*/
|
||||
static inline void fscache_end_io(struct fscache_retrieval *op,
|
||||
struct page *page, int error)
|
||||
{
|
||||
op->end_io_func(page, op->context, error);
|
||||
}
|
||||
|
||||
/*
|
||||
* out-of-line cache backend functions
|
||||
*/
|
||||
extern void fscache_init_cache(struct fscache_cache *cache,
|
||||
const struct fscache_cache_ops *ops,
|
||||
const char *idfmt,
|
||||
...) __attribute__ ((format (printf, 3, 4)));
|
||||
|
||||
extern int fscache_add_cache(struct fscache_cache *cache,
|
||||
struct fscache_object *fsdef,
|
||||
const char *tagname);
|
||||
extern void fscache_withdraw_cache(struct fscache_cache *cache);
|
||||
|
||||
extern void fscache_io_error(struct fscache_cache *cache);
|
||||
|
||||
extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
|
||||
struct pagevec *pagevec);
|
||||
|
||||
extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
|
||||
const void *data,
|
||||
uint16_t datalen);
|
||||
|
||||
#endif /* _LINUX_FSCACHE_CACHE_H */
|
||||
Loading…
Add table
Add a link
Reference in a new issue