Messages in this thread | | | Subject | Re: [PATCH] btrfs: resume qgroup rescan on rw remount | From | Nikolay Borisov <> | Date | Mon, 10 Jul 2017 16:12:43 +0300 |
| |
On 4.07.2017 14:49, Aleksa Sarai wrote: > 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: <stable@vger.kernel.org> # v3.11+ > Cc: Jeff Mahoney <jeffm@suse.com> > Fixes: b382a324b60f ("Btrfs: fix qgroup rescan resume on mount") > Signed-off-by: Aleksa Sarai <asarai@suse.de>
Indeed, looking at the code it seems that b382a324b60f ("Btrfs: fix qgroup rescan resume on mount") missed adding the qgroup_rescan_resume in the remount path. One thing which I couldn't verify though is whether reading fs_info->qgroup_flags without any locking is safe from remount context.
During remount I don't see any locks taken that prevent operations which can modify qgroup_flags.
> --- > fs/btrfs/super.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c > index 6346876c97ea..ff6690389343 100644 > --- a/fs/btrfs/super.c > +++ b/fs/btrfs/super.c > @@ -1821,6 +1821,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data) > 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); >
| |