Re: No SysRq remount because sb->s_bdev is NULL

[Florian Albrechtskirchinger <falbrechtskirchinger@gmail.com>]

On Saturday, July 28, 2012 15:46:50 Andreas Philipp wrote:
> On 28.07.2012 15:41, Florian Albrechtskirchinger wrote:
> > During a SysRq emergency remount Btrfs mounts are not remounted. I tracked
> > the issue down to this line in do_emergency_remount() in fs/super.c:
> > if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
> > 	!(sb->s_flags & MS_RDONLY))
> > s_bdev is NULL for Btrfs super blocks and subsequently do_remount_sb() is
> > never called. I couldn't think of a solution, besides resorting to an ugly
> > strcmp(sb->s_type->name, "btrfs"), without adding a field to struct
> > super_block or similar changes.
> > Thoughts?
>
> Just a first thought. Is there a possibility to write a dummy value into
> sb->s_bdev for btrfs super blocks. Thus it will not be NULL and
> everything in do_emergency_remount() in fs/super.c will work as wanted.

Then other code paths testing sb->s_bdev for NULL and assuming a non-NULL sb-
>s_bdev is a valid block device would fail.

    Flo