Re: [PATCH] fix mount -a on btrfs bind mount

[David Sterba <dsterba@suse.cz>]

On Wed, Dec 02, 2015 at 01:51:17PM +0100, Karel Zak wrote:
> On Fri, Nov 27, 2015 at 06:15:41PM +0100, Stanislav Brabec wrote:
> > root has to be literally the same as src_root, which is already the path
> > prefixed by /{subvolume}. Otherwise it will not match in
> > mnt_fs_streq_target(fs, xtgt) inside mnt_table_is_fs_mounted() and
> > repeated "mount -a" will mount it again and again.
> 
> yes
> 
> >  		if (src_root && !startswith(root, src_root)) {
> > -			size_t sz = strlen(root) + strlen(src_root) + 1;
> > -			char *tmp = malloc(sz);
> > -
> > +			char *tmp = strdup (src_root);
> >  			if (!tmp)
> >  				goto err;
> > -			snprintf(tmp, sz, "%s%s", src_root, root);
> >  			free(root);
> >  			root = tmp;
> >  		}
> 
> but this code is there for another use case. The problem is when the
> fstab_fs source is *sub-directory* on btrfs subvolume (or another bind
> mount). For example imagine:
> 
>   /dev/sdc        /mnt/test       btrfs   subvol=/anydir

Only subvolumes are accepted as parameter for 'subvol=', otherwise bind
mount needs to be used.