tree b74e7e863b7d7c2e116dc6754d8faf701c0aa3c9
parent 6af021d8fc3bcce790e7fbb391e39c5920fa3f71
author Liu Bo <liubo2009@cn.fujitsu.com> 1328782661 +0800
committer David Sterba <dsterba@suse.cz> 1329320423 +0100

Btrfs: fix trim 0 bytes after a device delete

A user reported a bug of btrfs's trim, that is we will trim 0 bytes
after a device delete.

The reproducer:

$ mkfs.btrfs disk1
$ mkfs.btrfs disk2
$ mount disk1 /mnt
$ fstrim -v /mnt
$ btrfs device add disk2 /mnt
$ btrfs device del disk1 /mnt
$ fstrim -v /mnt

This is because after we delete the device, the block group may start from
a non-zero place, which will confuse trim to discard nothing.

Reported-by: Lutz Euler <lutz.euler@freenet.de>
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>