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Commit d4b4087c authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
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Btrfs: do a full search everytime in btrfs_search_old_slot 



While running some snashot aware defrag tests I noticed I was panicing every
once and a while in key_search.  This is because of the optimization that says
if we find a key at slot 0 it will be at slot 0 all the way down the rest of the
tree.  This isn't the case for btrfs_search_old_slot since it will likely replay
changes to a buffer if something has changed since we took our sequence number.
So short circuit this optimization by setting prev_cmp to -1 every time we call
key_search so we will do our normal binary search.  With this patch I am no
longer seeing the panics I was seeing before.  Thanks,

Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 06ea65a3

fs/btrfs/ctree.c

+6 −2
Original line number Diff line number Diff line
@@ -2758,7 +2758,7 @@ int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key, 
	int level;

	int lowest_unlock = 1;

	u8 lowest_level = 0;

	int prev_cmp;

	int prev_cmp = -1;



	lowest_level = p->lowest_level;

	WARN_ON(p->nodes[0] != NULL);
@@ -2769,7 +2769,6 @@ int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key, 
	}



again:

	prev_cmp = -1;

	b = get_old_root(root, time_seq);

	level = btrfs_header_level(b);

	p->locks[level] = BTRFS_READ_LOCK;
@@ -2787,6 +2786,11 @@ int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key, 
		 */

		btrfs_unlock_up_safe(p, level + 1);



		/*

		 * Since we can unwind eb's we want to do a real search every

		 * time.

		 */

		prev_cmp = -1;

		ret = key_search(b, key, level, &prev_cmp, &slot);



		if (level != 0) {