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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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9
Documentation/filesystems/caching/backend-api.txt
View File

@@ -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)

17
Documentation/filesystems/caching/netfs-api.txt
View File

@@ -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: