From 361c093d7f99c3f6cbb07d5c580ce778ab418c42 Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Fri, 11 Oct 2013 17:14:58 +0200 Subject: [PATCH] Btrfs: Wait for uuid-tree rebuild task on remount read-only If the user remounts the filesystem read-only while the uuid-tree scan and rebuild task is still running (this happens once after the filesystem was mounted with an old kernel, or when forced with the mount options), the remount should wait on the tasks completion before setting the filesystem read-only. Otherwise the background task continues to write to the filesystem which is apparently not what users expect. The reproducer: TEST_DEV=/dev/sdzzzzz1 TEST_MNT=/mnt mkfs.btrfs -f $TEST_DEV mount $TEST_DEV $TEST_MNT for i in `seq 50000`; do btrfs subvolume create ${TEST_MNT}/$i; done umount $TEST_MNT mount $TEST_DEV $TEST_MNT -o rescan_uuid_tree sleep 1 ps -elf | fgrep '[btrfs-uuid]' | grep -v grep mount $TEST_DEV $TEST_MNT -o ro,remount ps -elf | fgrep '[btrfs-uuid]' | grep -v grep sleep 1 umount $TEST_MNT Signed-off-by: Stefan Behrens Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/super.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 1f62c1ccab1f..02f552f11829 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1330,6 +1330,12 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data) * this also happens on 'umount -rf' or on shutdown, when * the filesystem is busy. */ + + /* wait for the uuid_scan task to finish */ + down(&fs_info->uuid_tree_rescan_sem); + /* avoid complains from lockdep et al. */ + up(&fs_info->uuid_tree_rescan_sem); + sb->s_flags |= MS_RDONLY; btrfs_dev_replace_suspend_for_unmount(fs_info); -- 2.30.2