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authorDavid Howells <dhowells@redhat.com>2013-08-21 17:29:38 -0400
committerDavid Howells <dhowells@redhat.com>2013-09-06 09:17:30 +0100
commitda9803bc8812f5bd3b26baaa90e515b843c65ff7 (patch)
tree889b39ec88863fb46606cf345eeb4fdf8a90a67e /Documentation/filesystems/caching
parent6e4664525b1db28f8c4e1130957f70a94c19213e (diff)
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: David Howells <dhowells@redhat.com> cc: Hongyi Jia <jiayisuse@gmail.com> cc: Milosz Tanski <milosz@adfin.com>
Diffstat (limited to 'Documentation/filesystems/caching')
-rw-r--r--Documentation/filesystems/caching/backend-api.txt9
-rw-r--r--Documentation/filesystems/caching/netfs-api.txt17
2 files changed, 22 insertions, 4 deletions
diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
index d78bab9622c6..277d1e810670 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 97e6c0ecc5ef..12b344251523 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: