[PATCH] ubifs: Add freeze support

[Hyunchul Lee]

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.

> 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.
> 
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-- 

Thanks,
Hyunchul