tree 2659e92649b19df4cd54a65eabd34f961f8d57f8
parent 78a017a2c92df9b571db0a55a016280f9019c65e
author Josef Bacik <jbacik@fb.com> 1410380445 -0400
committer Chris Mason <clm@fb.com> 1410986304 -0700

Btrfs: make fiemap not blow when you have lots of snapshots

We have been iterating all references for each extent we have in a file when we
do fiemap to see if it is shared.  This is fine when you have a few clones or a
few snapshots, but when you have 5k snapshots suddenly fiemap just sits there
and stares at you.  So add btrfs_check_shared which will use the backref walking
code but will short circuit as soon as it finds a root or inode that doesn't
match the one we currently have.  This makes fiemap on my testbox go from
looking at me blankly for a day to spitting out actual output in a reasonable
amount of time.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>