Re: [PATCH] xfs: prevent deadlock in xfs_qm_shake()

[Felix Blyakher <felixb@xxxxxxx>]

On May 29, 2009, at 2:25 PM, Christoph Hellwig wrote:

> On Fri, May 29, 2009 at 01:10:31PM -0500, Felix Blyakher wrote:
> > It's possible to recurse into filesystem from the memory
> > allocation, which deadlocks in xfs_qm_shake(). Add check
> > for __GFP_FS, and bailout if it is not set.
> >
> > Signed-off-by: Felix Blyakher <felixb@xxxxxxx>
> > Signed-off-by: Hedi Berriche <hedi@xxxxxxx>
> > ---
> > fs/xfs/linux-2.6/kmem.h |    2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/xfs/linux-2.6/kmem.h b/fs/xfs/linux-2.6/kmem.h
> > index af6843c..d8d2321 100644
> > --- a/fs/xfs/linux-2.6/kmem.h
> > +++ b/fs/xfs/linux-2.6/kmem.h
> > @@ -103,7 +103,7 @@ extern void *kmem_zone_zalloc(kmem_zone_t *,  
> > unsigned int __nocast);
> > static inline int
> > kmem_shake_allow(gfp_t gfp_mask)
> > {
> > -       return (gfp_mask & __GFP_WAIT) != 0;
> > +       return ((gfp_mask & __GFP_WAIT && gfp_mask & __GFP_FS) != 0;
> Looks good to me.  But this could be written simpler as:
>
>         return ((gfp_mask & (__GFP_WAIT|__GFP_FS)) != 0;
Yeah, sure. Weird it didn't occur to me :)

Thanks,
Felix