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Commit 22cd2e7d authored by Arne Jansen's avatar Arne Jansen Committed by Chris Mason
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Btrfs: fix race in run_clustered_refs 



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commit d1270cd9
Author: Arne Jansen <sensille@gmx.net>
Date:   Tue Sep 13 15:16:43 2011 +0200

     Btrfs: put back delayed refs that are too new

I added a window where the delayed_ref's head->ref_mod code can diverge
from the sum of the remaining refs, because we release the head->mutex
in the middle. This leads to btrfs_lookup_extent_info returning wrong
numbers. This patch fixes this by adjusting the head's ref_mod with each
delayed ref we run.

Signed-off-by: default avatarArne Jansen <sensille@gmx.net>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent b12a3b1e

fs/btrfs/extent-tree.c

+17 −0
Original line number Original line Diff line number Diff line
@@ -2318,6 +2318,23 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans, 
		ref->in_tree = 0;

		ref->in_tree = 0;

		rb_erase(&ref->rb_node, &delayed_refs->root);

		rb_erase(&ref->rb_node, &delayed_refs->root);

		delayed_refs->num_entries--;

		delayed_refs->num_entries--;

		if (locked_ref) {

			/*

			 * when we play the delayed ref, also correct the

			 * ref_mod on head

			 */

			switch (ref->action) {

			case BTRFS_ADD_DELAYED_REF:

			case BTRFS_ADD_DELAYED_EXTENT:

				locked_ref->node.ref_mod -= ref->ref_mod;

				break;

			case BTRFS_DROP_DELAYED_REF:

				locked_ref->node.ref_mod += ref->ref_mod;

				break;

			default:

				WARN_ON(1);

			}

		}

		spin_unlock(&delayed_refs->lock);

		spin_unlock(&delayed_refs->lock);





		ret = run_one_delayed_ref(trans, root, ref, extent_op,

		ret = run_one_delayed_ref(trans, root, ref, extent_op,