FS-Cache: Provide proper invalidation

Provide a proper invalidation method rather than relying on the netfs retiring
the cookie it has and getting a new one.  The problem with this is that isn't
easy for the netfs to make sure that it has completed/cancelled all its
outstanding storage and retrieval operations on the cookie it is retiring.

Instead, have the cache provide an invalidation method that will cancel or wait
for all currently outstanding operations before invalidating the cache, and
will cause new operations to queue up behind that.  Whilst invalidation is in
progress, some requests will be rejected until the cache can stack a barrier on
the operation queue to cause new operations to be deferred behind it.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 748f9553c2cb..c58dbe613266 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -324,6 +324,38 @@ int fscache_cancel_op(struct fscache_operation *op)
 }
 
 /*
+ * Cancel all pending operations on an object
+ */
+void fscache_cancel_all_ops(struct fscache_object *object)
+{
+        struct fscache_operation *op;
+
+        _enter("OBJ%x", object->debug_id);
+
+        spin_lock(&object->lock);
+
+        while (!list_empty(&object->pending_ops)) {
+                op = list_entry(object->pending_ops.next,
+                                struct fscache_operation, pend_link);
+                fscache_stat(&fscache_n_op_cancelled);
+                list_del_init(&op->pend_link);
+
+                ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
+                op->state = FSCACHE_OP_ST_CANCELLED;
+
+                if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
+                        object->n_exclusive--;
+                if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+                        wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+                fscache_put_operation(op);
+                cond_resched_lock(&object->lock);
+        }
+
+        spin_unlock(&object->lock);
+        _leave("");
+}
+
+/*
  * Record the completion of an in-progress operation.
  */
 void fscache_op_complete(struct fscache_operation *op)