quota: Fix deadlock with suspend and quotas (dcdbed85) · Commits · 戴 / test

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>

fs/quota/quota.c

+21 −3

Original line number	Diff line number	Diff line
		@@ -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;
		@@ -309,6 +324,9 @@ static struct super_block quotactl_block(const char __user special)
		putname(tmp);
		if (IS_ERR(bdev))
		return ERR_CAST(bdev);
		if (quotactl_cmd_write(cmd))
		sb = get_super_thawed(bdev);
		else
		sb = get_super(bdev);
		bdput(bdev);
		if (!sb)
		@@ -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;

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