diff options
| author | Jan Kara <jack@suse.cz> | 2012-02-10 11:03:01 +0100 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2012-02-13 20:45:39 -0500 |
| commit | dcdbed853d9fbb0547b781ba676049b87f54129a (patch) | |
| tree | 6f8f2382e7aef99ec21ae9c4dfbfe18e47d4626c /fs | |
| parent | 6b6dc836a195e077e76977b6c020a73de411b46d (diff) | |
| download | linux-dcdbed853d9fbb0547b781ba676049b87f54129a.tar.bz2 | |
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>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/quota/quota.c | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/fs/quota/quota.c b/fs/quota/quota.c index 7898cd688a00..fc2c4388d126 100644 --- a/fs/quota/quota.c +++ b/fs/quota/quota.c @@ -292,11 +292,26 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id, } } +/* Return 1 if 'cmd' will block on frozen filesystem */ +static int quotactl_cmd_write(int cmd) +{ + switch (cmd) { + case Q_GETFMT: + case Q_GETINFO: + case Q_SYNC: + case Q_XGETQSTAT: + case Q_XGETQUOTA: + case Q_XQUOTASYNC: + return 0; + } + return 1; +} + /* * look up a superblock on which quota ops will be performed * - use the name of a block device to find the superblock thereon */ -static struct super_block *quotactl_block(const char __user *special) +static struct super_block *quotactl_block(const char __user *special, int cmd) { #ifdef CONFIG_BLOCK struct block_device *bdev; @@ -309,7 +324,10 @@ static struct super_block *quotactl_block(const char __user *special) putname(tmp); if (IS_ERR(bdev)) return ERR_CAST(bdev); - sb = get_super(bdev); + if (quotactl_cmd_write(cmd)) + sb = get_super_thawed(bdev); + else + sb = get_super(bdev); bdput(bdev); if (!sb) return ERR_PTR(-ENODEV); @@ -361,7 +379,7 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special, pathp = &path; } - sb = quotactl_block(special); + sb = quotactl_block(special, cmds); if (IS_ERR(sb)) { ret = PTR_ERR(sb); goto out; |