On Thu, May 17, 2018 at 03:16:51PM +0800, Anand Jain wrote: > We set the BTRFS_BALANCE_RESUME flag in the btrfs_recover_balance() > only, which isn't called during the remount. So when resuming from > the paused balance we hit the BUG. > > kernel: kernel BUG at fs/btrfs/volumes.c:3890! > :: > kernel: balance_kthread+0x51/0x60 [btrfs] > kernel: kthread+0x111/0x130 > :: > kernel: RIP: btrfs_balance+0x12e1/0x1570 [btrfs] RSP: ffffba7d0090bde8 > > Reproducer: > On a mounted BTRFS. > > btrfs balance start --full-balance /btrfs > btrfs balance pause /btrfs > mount -o remount,ro /dev/sdb /btrfs > mount -o remount,rw /dev/sdb /btrfs > > To fix this set the BTRFS_BALANCE_RESUME flag in btrfs_resume_balance_async(). > > Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> > --- > v2->v3: . Hold fs_info->balance_lock because in remount context there can > be more the one thread accessing the balance_ctl. > . Don't remove the BTRFS_BALANCE_RESUME set at recover_balance > as in the original code. > . Add comments. > v1->v2: btrfs_resume_balance_async() can be called only from remount or > mount, we don't need to hold fs_info->balance_lock. > > fs/btrfs/volumes.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 40e4259bdd51..c68976856d87 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -4112,6 +4112,15 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info) > return 0; > } > > + /* > + * A remount ro->rw sequence should continue with the > + * paused balance irrespective of who pauses it, system or > + * the user as of now, so set the resume flag. > + */ Please format comments to full 80 column width. Fixed. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
