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>
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 @@
/* 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 @@
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 @@
}
/**
+ * 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
*