From: Jan Kara <jack@suse.cz>
Date: Fri, 10 Feb 2012 10:03:01 +0000 (+0100)
Subject: quota: Fix deadlock with suspend and quotas
X-Git-Tag: v3.3-rc5~30^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dcdbed853d9fbb0547b781ba676049b87f54129a;p=pandora-kernel.git

quota: Fix deadlock with suspend and quotas

This script causes a kernel deadlock:
set -e
DEVICE=/dev/vg1/linear
lvchange -ay $DEVICE
mkfs.ext3 $DEVICE
mount -t ext3 -o usrquota,grpquota $DEVICE /mnt/test
quotacheck -gu /mnt/test
umount /mnt/test
mount -t ext3 -o usrquota,grpquota $DEVICE /mnt/test
quotaon /mnt/test
dmsetup suspend $DEVICE
setquota -u root 1 2 3 4 /mnt/test &
sleep 1
dmsetup resume $DEVICE

setquota acquired semaphore s_umount for read and then tried to perform a
transaction (and waits because the device is suspended).  dmsetup resume tries
to acquire s_umount for write before resuming the device (and waits for
setquota).

Fix the deadlock by grabbing a thawed superblock for quota commands which need
it.

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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