Re: [PATCH] ceph: init the i_list/g_list for cap flush

[Ilya Dryomov <idryomov@gmail.com>]

On Wed, Aug 25, 2021 at 12:50 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Wed, 2021-08-25 at 13:22 +0800, xiubli@redhat.com wrote:
> > From: Xiubo Li <xiubli@redhat.com>
> >
> > Always init the i_list/g_list in the begining to make sure it won't
> > crash the kernel if someone want to delete the cap_flush from the
> > lists.
> >
> > Cc: stable@vger.kernel.org
> > URL: https://tracker.ceph.com/issues/52401
> > Signed-off-by: Xiubo Li <xiubli@redhat.com>
> > ---
> >  fs/ceph/caps.c | 2 +-
> >  fs/ceph/snap.c | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > index 4f0dbc640b0b..60f60260cf42 100644
> > --- a/fs/ceph/caps.c
> > +++ b/fs/ceph/caps.c
> > @@ -3666,7 +3666,7 @@ static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,
> >       while (!list_empty(&to_remove)) {
> >               cf = list_first_entry(&to_remove,
> >                                     struct ceph_cap_flush, i_list);
> > -             list_del(&cf->i_list);
> > +             list_del_init(&cf->i_list);
> >               if (!cf->is_capsnap)
> >                       ceph_free_cap_flush(cf);
> >       }
> > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > index 62fab59bbf96..b41e6724c591 100644
> > --- a/fs/ceph/snap.c
> > +++ b/fs/ceph/snap.c
> > @@ -488,6 +488,8 @@ static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
> >               return;
> >       }
> >       capsnap->cap_flush.is_capsnap = true;
> > +     INIT_LIST_HEAD(&capsnap->cap_flush.i_list);
> > +     INIT_LIST_HEAD(&capsnap->cap_flush.g_list);
> >
> >       spin_lock(&ci->i_ceph_lock);
> >       used = __ceph_caps_used(ci);
>
> I'm not certain the second hunk is strictly needed. These either end up
> on the list or they just get freed. That said, they shouldn't hurt
> anything and it is more consistent. Merged into testing.
>
> Ilya, since this is marked for stable, this probably ought to go to
> Linus in the last v5.14 pile.

I'm inclined to fold this into "ceph: correctly handle releasing an
embedded cap flush" which is already queued for 5.14.

Thanks,

                Ilya