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![David Howells](/assets/img/avatar_default.png)
Now that the retrieval operation may be disposed of by fscache_put_operation() before we actually set the context, the retrieval-specific cleanup operation can produce a NULL-pointer dereference when it tries to unconditionally clean up the netfs context. Given that it is expected that we'll get at least as far as the place where we currently set the context pointer and it is unlikely we'll go through the error handling paths prior to that point, retain the context right from the point that the retrieval op is allocated. Concomitant to this, we need to retain the cookie pointer in the retrieval op also so that we can call the netfs to release its context in the release method. In addition, we might now get into fscache_release_retrieval_op() with the op only initialised. To this end, set the operation to DEAD only after the release method has been called and skip the n_pages test upon cleanup if the op is still in the INITIALISED state. Without these changes, the following oops might be seen: BUG: unable to handle kernel NULL pointer dereference at 00000000000000b8 ... RIP: 0010:[<ffffffffa0089c98>] fscache_release_retrieval_op+0xae/0x100 ... Call Trace: [<ffffffffa0088560>] fscache_put_operation+0x117/0x2e0 [<ffffffffa008b8f5>] __fscache_read_or_alloc_pages+0x351/0x3ac [<ffffffffa00b761f>] __nfs_readpages_from_fscache+0x59/0xbf [nfs] [<ffffffffa00b06c5>] nfs_readpages+0x10c/0x185 [nfs] [<ffffffff81124925>] ? alloc_pages_current+0x119/0x13e [<ffffffff810ee5fd>] ? __page_cache_alloc+0xfb/0x10a [<ffffffff810f87f8>] __do_page_cache_readahead+0x188/0x22c [<ffffffff810f8b3a>] ondemand_readahead+0x29e/0x2af [<ffffffff810f8c92>] page_cache_sync_readahead+0x38/0x3a [<ffffffff810ef337>] generic_file_read_iter+0x1a2/0x55a [<ffffffffa00a9dff>] ? nfs_revalidate_mapping+0xd6/0x288 [nfs] [<ffffffffa00a6a23>] nfs_file_read+0x49/0x70 [nfs] [<ffffffff811363be>] new_sync_read+0x78/0x9c [<ffffffff81137164>] __vfs_read+0x13/0x38 [<ffffffff8113721e>] vfs_read+0x95/0x121 [<ffffffff811372f6>] SyS_read+0x4c/0x8a [<ffffffff81557a52>] system_call_fastpath+0x12/0x17 Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Steve Dickson <steved@redhat.com> Acked-by: Jeff Layton <jeff.layton@primarydata.com>
553 lines
18 KiB
C
553 lines
18 KiB
C
/* 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/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_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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bool (*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
|
|
* @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_l = 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);
|
|
}
|
|
|
|
static inline void __fscache_use_cookie(struct fscache_cookie *cookie)
|
|
{
|
|
atomic_inc(&cookie->n_active);
|
|
}
|
|
|
|
/**
|
|
* fscache_use_cookie - Request usage of cookie attached to an object
|
|
* @object: Object description
|
|
*
|
|
* Request usage of the cookie attached to an object. NULL is returned if the
|
|
* relinquishment had reduced the cookie usage count to 0.
|
|
*/
|
|
static inline bool fscache_use_cookie(struct fscache_object *object)
|
|
{
|
|
struct fscache_cookie *cookie = object->cookie;
|
|
return atomic_inc_not_zero(&cookie->n_active) != 0;
|
|
}
|
|
|
|
static inline bool __fscache_unuse_cookie(struct fscache_cookie *cookie)
|
|
{
|
|
return atomic_dec_and_test(&cookie->n_active);
|
|
}
|
|
|
|
static inline void __fscache_wake_unused_cookie(struct fscache_cookie *cookie)
|
|
{
|
|
wake_up_atomic_t(&cookie->n_active);
|
|
}
|
|
|
|
/**
|
|
* fscache_unuse_cookie - Cease usage of cookie attached to an object
|
|
* @object: Object description
|
|
*
|
|
* Cease usage of the cookie attached to an object. When the users count
|
|
* reaches zero then the cookie relinquishment will be permitted to proceed.
|
|
*/
|
|
static inline void fscache_unuse_cookie(struct fscache_object *object)
|
|
{
|
|
struct fscache_cookie *cookie = object->cookie;
|
|
if (__fscache_unuse_cookie(cookie))
|
|
__fscache_wake_unused_cookie(cookie);
|
|
}
|
|
|
|
/*
|
|
* out-of-line cache backend functions
|
|
*/
|
|
extern __printf(3, 4)
|
|
void fscache_init_cache(struct fscache_cache *cache,
|
|
const struct fscache_cache_ops *ops,
|
|
const char *idfmt, ...);
|
|
|
|
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_page_cached(struct fscache_retrieval *op,
|
|
struct page *page);
|
|
|
|
extern void fscache_mark_pages_cached(struct fscache_retrieval *op,
|
|
struct pagevec *pagevec);
|
|
|
|
extern bool fscache_object_sleep_till_congested(signed long *timeoutp);
|
|
|
|
extern enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
|
|
const void *data,
|
|
uint16_t datalen);
|
|
|
|
extern void fscache_object_retrying_stale(struct fscache_object *object);
|
|
|
|
enum fscache_why_object_killed {
|
|
FSCACHE_OBJECT_IS_STALE,
|
|
FSCACHE_OBJECT_NO_SPACE,
|
|
FSCACHE_OBJECT_WAS_RETIRED,
|
|
FSCACHE_OBJECT_WAS_CULLED,
|
|
};
|
|
extern void fscache_object_mark_killed(struct fscache_object *object,
|
|
enum fscache_why_object_killed why);
|
|
|
|
#endif /* _LINUX_FSCACHE_CACHE_H */
|