Btrfs: fix race when updating existing ref head (21543bad) · Commits · 戴 / test

While we update an existing ref head's extent_op, we're not holding its spinlock, so while we're updating its extent_op contents (key, flags) we can have a task running __btrfs_run_delayed_refs() that holds the ref head's lock and sets its extent_op to NULL right after the task updating the ref head just checked its extent_op was not NULL. Signed-off-by:

Filipe David Borba Manana <fdmanana@gmail.com> Signed-off-by:

Chris Mason <clm@fb.com>

fs/btrfs/delayed-ref.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -495,6 +495,7 @@ update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
		ref = btrfs_delayed_node_to_head(update);
		BUG_ON(existing_ref->is_data != ref->is_data);

		spin_lock(&existing_ref->lock);
		if (ref->must_insert_reserved) {
		/* if the extent was freed and then
		* reallocated before the delayed ref
		@@ -536,7 +537,6 @@ update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
		* only need the lock for this case cause we could be processing it
		* currently, for refs we just added we know we're a-ok.
		*/
		spin_lock(&existing_ref->lock);
		existing->ref_mod += update->ref_mod;
		spin_unlock(&existing_ref->lock);
		}

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