Commit d4b4087c authored Sep 24, 2013 by Josef Bacik Committed by Chris Mason Nov 11, 2013

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: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris 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 @@ again:
		*/
		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) {

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