From: Li Zefan <lizf@cn.fujitsu.com>
Date: Tue, 7 Dec 2010 01:51:26 +0000 (+0000)
Subject: Btrfs: Fix a crash when mounting a subvolume
X-Git-Tag: v2.6.37-rc6~30^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f106e82caaa0d943e47cacc184f5b40d538e0044;p=pandora-kernel.git

Btrfs: Fix a crash when mounting a subvolume

We should drop dentry before deactivating the superblock, otherwise
we can hit this bug:

BUG: Dentry f349a690{i=100,n=/} still in use (1) [unmount of btrfs loop1]
...

Steps to reproduce the bug:

  # mount /dev/loop1 /mnt
  # mkdir save
  # btrfs subvolume snapshot /mnt save/snap1
  # umount /mnt
  # mount -o subvol=save/snap1 /dev/loop1 /mnt
  (crash)

Reported-by: Michael Niederle <mniederle@gmx.at>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
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