4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Aleksa Sarai <asa...@suse.de> commit 6c6b5a39c4bf3dbd8cf629c9f5450e983c19dbb9 upstream. Several distributions mount the "proper root" as ro during initrd and then remount it as rw before pivot_root(2). Thus, if a rescan had been aborted by a previous shutdown, the rescan would never be resumed. This issue would manifest itself as several btrfs ioctl(2)s causing the entire machine to hang when btrfs_qgroup_wait_for_completion was hit (due to the fs_info->qgroup_rescan_running flag being set but the rescan itself not being resumed). Notably, Docker's btrfs storage driver makes regular use of BTRFS_QUOTA_CTL_DISABLE and BTRFS_IOC_QUOTA_RESCAN_WAIT (causing this problem to be manifested on boot for some machines). Cc: Jeff Mahoney <je...@suse.com> Fixes: b382a324b60f ("Btrfs: fix qgroup rescan resume on mount") Signed-off-by: Aleksa Sarai <asa...@suse.de> Reviewed-by: Nikolay Borisov <nbori...@suse.com> Tested-by: Nikolay Borisov <nbori...@suse.com> Signed-off-by: David Sterba <dste...@suse.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- fs/btrfs/super.c | 2 ++ 1 file changed, 2 insertions(+) --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1834,6 +1834,8 @@ static int btrfs_remount(struct super_bl goto restore; } + btrfs_qgroup_rescan_resume(fs_info); + if (!fs_info->uuid_root) { btrfs_info(fs_info, "creating UUID tree"); ret = btrfs_create_uuid_tree(fs_info);