On Tue, 10 Jun 2014 16:48:28 -0400
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
> On Tue, Jun 10, 2014 at 04:14:35PM -0400, Jeff Layton wrote:
> > break_deleg is subject to the same potential race as break_lease. Add
> > a memory barrier to prevent it.
>
> Acked-by: J. Bruce Fields <bfields@xxxxxxxxxx>
>
> Though we might now just move the comment, smp_mb(), and inode->i_flock
> calls into __break_lease?
>
> --b.
>
We certainly could, but it would mean they'd no longer be inlined. I
doubt it'd make much difference, but I'm inclined to leave them as
inlines for now.
> >
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> > ---
> > include/linux/fs.h | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index c3f46e499dd0..22ae79650b82 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -1914,6 +1914,12 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
> >
> > static inline int break_deleg(struct inode *inode, unsigned int mode)
> > {
> > + /*
> > + * Since this check is lockless, we must ensure that any refcounts
> > + * taken are done before checking inode->i_flock. Otherwise, we could
> > + * end up racing with tasks trying to set a new lease on this file.
> > + */
> > + smp_mb();
> > if (inode->i_flock)
> > return __break_lease(inode, mode, FL_DELEG);
> > return 0;
> > --
> > 1.9.3
> >
--
Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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