Re: [PATCH 6/6] efivarfs: fix error on write to new variable leaving remnants

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Sun, 2024-12-22 at 11:12 +0100, Christian Brauner wrote:
> > Do the fs people have a preference? The cursor mark is simpler to
> > implement but depends on internal libfs.c magic. The actor hijack
> > is at least something that already exists, so would be less prone
> > to breaking due to internal changes.
> 
> I think making this filesystem specific is better than plumbing this
> into dcache_readdir().

Neither would require changes to libfs.c: the dcache_readdir already
does the ignore cursor behaviour; the code in efivarfs would just set
the cursor flag to take advantage of it.

However, on further consideration I think making the zero size entries
not show up in the directory listing doesn't really help anything: they
still have to be found on lookup (otherwise nothing mediates a same
variable create race) which means an open by name from userspace will
still get hold of one.  The good news is that after this change they
should only show up fleetingly instead of hanging around until the next
reboot, so the chances of anyone hitting a problem is much smaller.

Regards,

James