Commit da9803bc authored by David Howells's avatar David Howells

FS-Cache: Add interface to check consistency of a cached object

Extend the fscache netfs API so that the netfs can ask as to whether a cache
object is up to date with respect to its corresponding netfs object:

	int fscache_check_consistency(struct fscache_cookie *cookie)

This will call back to the netfs to check whether the auxiliary data associated
with a cookie is correct.  It returns 0 if it is and -ESTALE if it isn't; it
may also return -ENOMEM and -ERESTARTSYS.

The backends now have to implement a mandatory operation pointer:

	int (*check_consistency)(struct fscache_object *object)

that corresponds to the above API call.  FS-Cache takes care of pinning the
object and the cookie in memory and managing this call with respect to the
object state.

Original-author: Hongyi Jia <jiayisuse@gmail.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Hongyi Jia <jiayisuse@gmail.com>
cc: Milosz Tanski <milosz@adfin.com>
parent 6e466452
......@@ -299,6 +299,15 @@ performed on the denizens of the cache. These are held in a structure of type:
enough space in the cache to permit this.
(*) Check coherency state of an object [mandatory]:
int (*check_consistency)(struct fscache_object *object)
This method is called to have the cache check the saved auxiliary data of
the object against the netfs's idea of the state. 0 should be returned
if they're consistent and -ESTALE otherwise. -ENOMEM and -ERESTARTSYS
may also be returned.
(*) Update object [mandatory]:
int (*update_object)(struct fscache_object *object)
......
......@@ -32,7 +32,7 @@ This document contains the following sections:
(9) Setting the data file size
(10) Page alloc/read/write
(11) Page uncaching
(12) Index and data file update
(12) Index and data file consistency
(13) Miscellaneous cookie operations
(14) Cookie unregistration
(15) Index invalidation
......@@ -690,9 +690,18 @@ written to the cache and for the cache to finish with the page generally. No
error is returned.
==========================
INDEX AND DATA FILE UPDATE
==========================
===============================
INDEX AND DATA FILE CONSISTENCY
===============================
To find out whether auxiliary data for an object is up to data within the
cache, the following function can be called:
int fscache_check_consistency(struct fscache_cookie *cookie)
This will call back to the netfs to check whether the auxiliary data associated
with a cookie is correct. It returns 0 if it is and -ESTALE if it isn't; it
may also return -ENOMEM and -ERESTARTSYS.
To request an update of the index data for an index or other object, the
following function should be called:
......
......@@ -558,3 +558,74 @@ void __fscache_cookie_put(struct fscache_cookie *cookie)
_leave("");
}
/*
* check the consistency between the netfs inode and the backing cache
*
* NOTE: it only serves no-index type
*/
int __fscache_check_consistency(struct fscache_cookie *cookie)
{
struct fscache_operation *op;
struct fscache_object *object;
int ret;
_enter("%p,", cookie);
ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE);
if (fscache_wait_for_deferred_lookup(cookie) < 0)
return -ERESTARTSYS;
if (hlist_empty(&cookie->backing_objects))
return 0;
op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
if (!op)
return -ENOMEM;
fscache_operation_init(op, NULL, NULL);
op->flags = FSCACHE_OP_MYTHREAD |
(1 << FSCACHE_OP_WAITING);
spin_lock(&cookie->lock);
if (hlist_empty(&cookie->backing_objects))
goto inconsistent;
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);
if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
goto inconsistent;
op->debug_id = atomic_inc_return(&fscache_op_debug_id);
atomic_inc(&cookie->n_active);
if (fscache_submit_op(object, op) < 0)
goto submit_failed;
/* the work queue now carries its own ref on the object */
spin_unlock(&cookie->lock);
ret = fscache_wait_for_operation_activation(object, op,
NULL, NULL, NULL);
if (ret == 0) {
/* ask the cache to honour the operation */
ret = object->cache->ops->check_consistency(op);
fscache_op_complete(op, false);
} else if (ret == -ENOBUFS) {
ret = 0;
}
fscache_put_operation(op);
_leave(" = %d", ret);
return ret;
submit_failed:
atomic_dec(&cookie->n_active);
inconsistent:
spin_unlock(&cookie->lock);
kfree(op);
_leave(" = -ESTALE");
return -ESTALE;
}
EXPORT_SYMBOL(__fscache_check_consistency);
......@@ -130,6 +130,12 @@ extern void fscache_operation_gc(struct work_struct *);
/*
* page.c
*/
extern int fscache_wait_for_deferred_lookup(struct fscache_cookie *);
extern int fscache_wait_for_operation_activation(struct fscache_object *,
struct fscache_operation *,
atomic_t *,
atomic_t *,
void (*)(struct fscache_operation *));
extern void fscache_invalidate_writes(struct fscache_cookie *);
/*
......
......@@ -278,7 +278,7 @@ static struct fscache_retrieval *fscache_alloc_retrieval(
/*
* wait for a deferred lookup to complete
*/
static int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
{
unsigned long jif;
......@@ -322,41 +322,45 @@ static void fscache_do_cancel_retrieval(struct fscache_operation *_op)
/*
* wait for an object to become active (or dead)
*/
static int fscache_wait_for_retrieval_activation(struct fscache_object *object,
struct fscache_retrieval *op,
int fscache_wait_for_operation_activation(struct fscache_object *object,
struct fscache_operation *op,
atomic_t *stat_op_waits,
atomic_t *stat_object_dead)
atomic_t *stat_object_dead,
void (*do_cancel)(struct fscache_operation *))
{
int ret;
if (!test_bit(FSCACHE_OP_WAITING, &op->op.flags))
if (!test_bit(FSCACHE_OP_WAITING, &op->flags))
goto check_if_dead;
_debug(">>> WT");
if (stat_op_waits)
fscache_stat(stat_op_waits);
if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,
if (wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
fscache_wait_bit_interruptible,
TASK_INTERRUPTIBLE) != 0) {
ret = fscache_cancel_op(&op->op, fscache_do_cancel_retrieval);
ret = fscache_cancel_op(op, do_cancel);
if (ret == 0)
return -ERESTARTSYS;
/* it's been removed from the pending queue by another party,
* so we should get to run shortly */
wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,
wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
fscache_wait_bit, TASK_UNINTERRUPTIBLE);
}
_debug("<<< GO");
check_if_dead:
if (op->op.state == FSCACHE_OP_ST_CANCELLED) {
if (op->state == FSCACHE_OP_ST_CANCELLED) {
if (stat_object_dead)
fscache_stat(stat_object_dead);
_leave(" = -ENOBUFS [cancelled]");
return -ENOBUFS;
}
if (unlikely(fscache_object_is_dead(object))) {
pr_err("%s() = -ENOBUFS [obj dead %d]\n", __func__, op->op.state);
fscache_cancel_op(&op->op, fscache_do_cancel_retrieval);
pr_err("%s() = -ENOBUFS [obj dead %d]\n", __func__, op->state);
fscache_cancel_op(op, do_cancel);
if (stat_object_dead)
fscache_stat(stat_object_dead);
return -ENOBUFS;
}
......@@ -432,10 +436,11 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
/* we wait for the operation to become active, and then process it
* *here*, in this thread, and not in the thread pool */
ret = fscache_wait_for_retrieval_activation(
object, op,
ret = fscache_wait_for_operation_activation(
object, &op->op,
__fscache_stat(&fscache_n_retrieval_op_waits),
__fscache_stat(&fscache_n_retrievals_object_dead));
__fscache_stat(&fscache_n_retrievals_object_dead),
fscache_do_cancel_retrieval);
if (ret < 0)
goto error;
......@@ -557,10 +562,11 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
/* we wait for the operation to become active, and then process it
* *here*, in this thread, and not in the thread pool */
ret = fscache_wait_for_retrieval_activation(
object, op,
ret = fscache_wait_for_operation_activation(
object, &op->op,
__fscache_stat(&fscache_n_retrieval_op_waits),
__fscache_stat(&fscache_n_retrievals_object_dead));
__fscache_stat(&fscache_n_retrievals_object_dead),
fscache_do_cancel_retrieval);
if (ret < 0)
goto error;
......@@ -658,10 +664,11 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
fscache_stat(&fscache_n_alloc_ops);
ret = fscache_wait_for_retrieval_activation(
object, op,
ret = fscache_wait_for_operation_activation(
object, &op->op,
__fscache_stat(&fscache_n_alloc_op_waits),
__fscache_stat(&fscache_n_allocs_object_dead));
__fscache_stat(&fscache_n_allocs_object_dead),
fscache_do_cancel_retrieval);
if (ret < 0)
goto error;
......
......@@ -251,6 +251,10 @@ struct fscache_cache_ops {
/* unpin an object in the cache */
void (*unpin_object)(struct fscache_object *object);
/* check the consistency between the backing cache and the FS-Cache
* cookie */
bool (*check_consistency)(struct fscache_operation *op);
/* store the updated auxiliary data on an object */
void (*update_object)(struct fscache_object *object);
......
......@@ -183,6 +183,7 @@ extern struct fscache_cookie *__fscache_acquire_cookie(
const struct fscache_cookie_def *,
void *);
extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
extern int __fscache_check_consistency(struct fscache_cookie *);
extern void __fscache_update_cookie(struct fscache_cookie *);
extern int __fscache_attr_changed(struct fscache_cookie *);
extern void __fscache_invalidate(struct fscache_cookie *);
......@@ -325,6 +326,25 @@ void fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
__fscache_relinquish_cookie(cookie, retire);
}
/**
* fscache_check_consistency - Request that if the cache is updated
* @cookie: The cookie representing the cache object
*
* Request an consistency check from fscache, which passes the request
* to the backing cache.
*
* Returns 0 if consistent and -ESTALE if inconsistent. May also
* return -ENOMEM and -ERESTARTSYS.
*/
static inline
int fscache_check_consistency(struct fscache_cookie *cookie)
{
if (fscache_cookie_valid(cookie))
return __fscache_check_consistency(cookie);
else
return 0;
}
/**
* fscache_update_cookie - Request that a cache object be updated
* @cookie: The cookie representing the cache object
......
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