On Thu, Apr 28, 2016 at 11:12:20AM +0200, David Sterba wrote: > On Wed, Apr 27, 2016 at 04:22:17PM -0700, Liu Bo wrote: > > On Wed, Apr 27, 2016 at 05:14:36PM +0200, David Sterba wrote: > > > A user reported mount failures with EBUSY during boot, there's root > > > partition and many subvolumes, mounted via /etc/fstab. > > > > > > The failure depends on timing, when multiple subvolumes reach the code > > > between superblock creation in RO mode, while the subvolumes are RW. > > > This discrepancy leads to EBUSY and the code has been there since ages. > > > > > > If the subvolumes are mounted after a short delay, there's no EBUSY. > > > There's no missing locking, the supreblock creation is atomic and the > > > error code seems to be just artificial. We support different RO/RW > > > mounts in mount_subvol and do the relevant adjustments if the flags do > > > not match. > > > > Looks good to me. > > > > Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx> > > > > But What I'm worrying about is that mount_subvol() will help subvolume > > mounting get correct mount flags by calling btrfs_remount(), and > > btrfs_remount() can remove sb->s_flags's MS_RDONLY. In all syscall cases > > it's ok as we have mnt->mnt_flags, but for btrfs's add_dev ioctl, we > > don't check mnt_want_write_file() while btrfs's rm_dev ioctl does the > > check, should we add that for add_dev ioctl? > > That's right, I have patches to fix that and will send them. So, after a bit of refreshing, the patches are not finished, as add device must respect read only mount and seeding devices, that can turn RO to RW. And I got stuck in the device replace case, where we have to do the drop_mnt_write some time later. Not sure when I'll get to it, pushed to my git repos, branch fix/ioctl-want-write-local . -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html