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

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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: David Howells <dhowells@redhat.com>
cc: Hongyi Jia <jiayisuse@gmail.com>
cc: Milosz Tanski <milosz@adfin.com>
This commit is contained in:
David Howells
2013-08-21 17:29:38 -04:00
parent 6e4664525b
commit da9803bc88
7 changed files with 154 additions and 28 deletions
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55
fs/fscache/page.c
View File

@@ -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;
@@ -322,42 +322,46 @@ 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,
atomic_t *stat_op_waits,
atomic_t *stat_object_dead)
int fscache_wait_for_operation_activation(struct fscache_object *object,
struct fscache_operation *op,
atomic_t *stat_op_waits,
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");
fscache_stat(stat_op_waits);
if (wait_on_bit(&op->op.flags, FSCACHE_OP_WAITING,
if (stat_op_waits)
fscache_stat(stat_op_waits);
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) {
fscache_stat(stat_object_dead);
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);
fscache_stat(stat_object_dead);
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;
}
return 0;
@@ -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;