Re: [PATCH AUTOSEL 5.0 61/98] libceph: fix breakage caused by multipage bvecs

[Sasha Levin]

On Tue, Apr 23, 2019 at 10:28:56AM +0200, Ilya Dryomov wrote:
> On Mon, Apr 22, 2019 at 9:44 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Ilya Dryomov <idryomov@xxxxxxxxx>
> >
> > [ Upstream commit 187df76325af5d9e12ae9daec1510307797e54f0 ]
> >
> > A bvec can now consist of multiple physically contiguous pages.
> > This means that bvec_iter_advance() can move to a different page while
> > staying in the same bvec (i.e. ->bi_bvec_done != 0).
> >
> > The messenger works in terms of segments which can now be defined as
> > the smaller of a bvec and a page.  The "more bytes to process in this
> > segment" condition holds only if bvec_iter_advance() leaves us in the
> > same bvec _and_ in the same page.  On next bvec (possibly in the same
> > page) and on next page (possibly in the same bvec) we may need to set
> > ->last_piece.
> >
> > Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> > Signed-off-by: Sasha Levin (Microsoft) <sashal@xxxxxxxxxx>
> > ---
> >  net/ceph/messenger.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> > index 7e71b0df1fbc..3083988ce729 100644
> > --- a/net/ceph/messenger.c
> > +++ b/net/ceph/messenger.c
> > @@ -840,6 +840,7 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
> >                                         size_t bytes)
> >  {
> >         struct ceph_bio_iter *it = &cursor->bio_iter;
> > +       struct page *page = bio_iter_page(it->bio, it->iter);
> >
> >         BUG_ON(bytes > cursor->resid);
> >         BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
> > @@ -851,7 +852,8 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
> >                 return false;   /* no more data */
> >         }
> >
> > -       if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done))
> > +       if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done &&
> > +                      page == bio_iter_page(it->bio, it->iter)))
> >                 return false;   /* more bytes to process in this segment */
> >
> >         if (!it->iter.bi_size) {
> > @@ -899,6 +901,7 @@ static bool ceph_msg_data_bvecs_advance(struct ceph_msg_data_cursor *cursor,
> >                                         size_t bytes)
> >  {
> >         struct bio_vec *bvecs = cursor->data->bvec_pos.bvecs;
> > +       struct page *page = bvec_iter_page(bvecs, cursor->bvec_iter);
> >
> >         BUG_ON(bytes > cursor->resid);
> >         BUG_ON(bytes > bvec_iter_len(bvecs, cursor->bvec_iter));
> > @@ -910,7 +913,8 @@ static bool ceph_msg_data_bvecs_advance(struct ceph_msg_data_cursor *cursor,
> >                 return false;   /* no more data */
> >         }
> >
> > -       if (!bytes || cursor->bvec_iter.bi_bvec_done)
> > +       if (!bytes || (cursor->bvec_iter.bi_bvec_done &&
> > +                      page == bvec_iter_page(bvecs, cursor->bvec_iter)))
> >                 return false;   /* more bytes to process in this segment */
> >
> >         BUG_ON(cursor->last_piece);
>
> Same here, shouldn't be needed.

Dropped, thanks!

--
Thanks,
Sasha