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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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20
include/linux/fscache.h
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@@ -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