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/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 0e91a3c..318e843 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -558,3 +558,74 @@
_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);
+ fscache_op_complete(op, false);
+ } 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);