From dcdbed853d9fbb0547b781ba676049b87f54129a Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 10 Feb 2012 11:03:01 +0100 Subject: 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 Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/quota/quota.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/fs/quota/quota.c b/fs/quota/quota.c index 7898cd6..fc2c438 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; -- cgit v1.1