Re: [PATCH] ubifs: Add freeze support

Hyunchul Lee
2017-05-29T02:25:14Z

Hi, Richard.

On Mon, May 29, 2017 at 09:43:46AM +0900, Hyunchul Lee wrote:
> On Sat, May 27, 2017 at 01:23:38AM -0700, Christoph Hellwig wrote:
> > > +static int ubifs_freeze_super(struct super_block *sb)
> > > +{
> > > + struct ubifs_info *c = sb->s_fs_info;
> > > + int err;
> > > +
> > > + dbg_gen("starting");
> > > + /* freeze_super always succeeds if file system is in read-only.
> > > + * however if there are errors, UBIFS is switched to read-only mode.
> > > + * so @ro_error should be checked.
> > > + */
> > > + err = freeze_super(sb);
> > > + if (!err && c->ro_error) {
> > > + thaw_super(sb);
> > > + return -EIO;
> > > + }
> > > + return err;
> >
> > This is just broken. First ubifs should still properly propagate
> > the errors, and second freezing/unfreezing read only file systems is
> > perfectly valid,
>
> it is right.

if updating TNC is failed, ubifs might become inconsistant and be switched to
read-only mode. for example, when ubifs_jnl_update is called to create a file,
if inserting a znode for new inode is failed, TNC has only a znode for
new dentry. and this can be only recoverd by replay.

is it required to fix this?

>
> > and third the freeze_super method is a special
> > hack for gfs2 that should not gain additional users.
>
> I thought that it was ok. because commit 48b6bca says "every filesystem
> that implements this hooks must call the vfs freeze_super ..."
>
> Thank you for comment.
> >
> > ______________________________________________________
> > Linux MTD discussion mailing list
> > http://lists.infradead.org/mailman/listinfo/linux-mtd/
>
> --
>
> Thanks,
> Hyunchul

--

Thanks,
Hyunchul