Btrfs: do a full search everytime in btrfs_search_old_slot
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 <631dfb3d07694fdcf26abc7aac2c6c2b641f8bde@fusionio.com>
Signed-off-by: Chris Mason <a169954b4cb1a46cee25f659d3bddfebe02b5fba@fusionio.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs