[PATCH 1/8] FS-Cache: Add interface to check consistency of a cachedobject
From: David Howells
Date: Thu Sep 05 2013 - 18:21:17 EST
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@xxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Hongyi Jia <jiayisuse@xxxxxxxxx>
cc: Milosz Tanski <milosz@xxxxxxxxx>
---
Documentation/filesystems/caching/backend-api.txt | 9 +++
Documentation/filesystems/caching/netfs-api.txt | 17 +++--
fs/fscache/cookie.c | 69 +++++++++++++++++++++
fs/fscache/internal.h | 6 ++
fs/fscache/page.c | 55 +++++++++-------
include/linux/fscache-cache.h | 4 ++
include/linux/fscache.h | 20 ++++++
7 files changed, 152 insertions(+), 28 deletions(-)
diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
index d78bab9..277d1e8 100644
--- a/Documentation/filesystems/caching/backend-api.txt
+++ b/Documentation/filesystems/caching/backend-api.txt
@@ -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)
diff --git a/Documentation/filesystems/caching/netfs-api.txt b/Documentation/filesystems/caching/netfs-api.txt
index 97e6c0e..12b3442 100644
--- a/Documentation/filesystems/caching/netfs-api.txt
+++ b/Documentation/filesystems/caching/netfs-api.txt
@@ -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:
diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 0e91a3c..2ef4c9d 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -558,3 +558,72 @@ 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);
+ 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);
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 12d505b..4226f66 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -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 *);
/*
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index d479ab3..793e3d5 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -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;
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index a9ff9a3..7823e9e 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -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);
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 7a08623..d984aff 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -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 *);
@@ -326,6 +327,25 @@ void fscache_relinquish_cookie(struct fscache_cookie *cookie, int 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
*
--
1.7.9.5
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