On Tue, 2017-04-18 at 15:09 +0200, Ilya Dryomov wrote:
> On Tue, Apr 18, 2017 at 2:19 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > On Mon, 2017-04-17 at 12:42 -0400, Jeff Layton wrote:
> > > Cephfs can get cap update requests that contain a new epoch barrier in
> > > them. When that happens we want to pause all OSD traffic until the right
> > > map epoch arrives.
> > >
> > > Add an epoch_barrier field to ceph_osd_client that is protected by the
> > > osdc->lock rwsem. When the barrier is set, and the current OSD map
> > > epoch is below that, pause the request target when submitting the
> > > request or when revisiting it. Add a way for upper layers (cephfs)
> > > to update the epoch_barrier as well.
> > >
> > > If we get a new map, compare the new epoch against the barrier before
> > > kicking requests and request another map if the map epoch is still lower
> > > than the one we want.
> > >
> > > If we get a map with a full pool, or at quota condition, then set the
> > > barrier to the current epoch value.
> > >
> > > Reviewed-by: "Yan, Zheng” <zyan@xxxxxxxxxx>
> > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > Reviewed-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> > > ---
> > > include/linux/ceph/osd_client.h | 2 ++
> > > net/ceph/debugfs.c | 3 +-
> > > net/ceph/osd_client.c | 76 ++++++++++++++++++++++++++++++++++++-----
> > > 3 files changed, 72 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> > > index 8cf644197b1a..85650b415e73 100644
> > > --- a/include/linux/ceph/osd_client.h
> > > +++ b/include/linux/ceph/osd_client.h
> > > @@ -267,6 +267,7 @@ struct ceph_osd_client {
> > > struct rb_root osds; /* osds */
> > > struct list_head osd_lru; /* idle osds */
> > > spinlock_t osd_lru_lock;
> > > + u32 epoch_barrier;
> > > struct ceph_osd homeless_osd;
> > > atomic64_t last_tid; /* tid of last request */
> > > u64 last_linger_id;
> > > @@ -305,6 +306,7 @@ extern void ceph_osdc_handle_reply(struct ceph_osd_client *osdc,
> > > struct ceph_msg *msg);
> > > extern void ceph_osdc_handle_map(struct ceph_osd_client *osdc,
> > > struct ceph_msg *msg);
> > > +void ceph_osdc_update_epoch_barrier(struct ceph_osd_client *osdc, u32 eb);
> > >
> > > extern void osd_req_op_init(struct ceph_osd_request *osd_req,
> > > unsigned int which, u16 opcode, u32 flags);
> > > diff --git a/net/ceph/debugfs.c b/net/ceph/debugfs.c
> > > index d7e63a4f5578..71ba13927b3d 100644
> > > --- a/net/ceph/debugfs.c
> > > +++ b/net/ceph/debugfs.c
> > > @@ -62,7 +62,8 @@ static int osdmap_show(struct seq_file *s, void *p)
> > > return 0;
> > >
> > > down_read(&osdc->lock);
> > > - seq_printf(s, "epoch %d flags 0x%x\n", map->epoch, map->flags);
> > > + seq_printf(s, "epoch %u barrier %u flags 0x%x\n", map->epoch,
> > > + osdc->epoch_barrier, map->flags);
> > >
> > > for (n = rb_first(&map->pg_pools); n; n = rb_next(n)) {
> > > struct ceph_pg_pool_info *pi =
> > > diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> > > index 55b7585ccefd..beeac4f39aa5 100644
> > > --- a/net/ceph/osd_client.c
> > > +++ b/net/ceph/osd_client.c
> > > @@ -1298,8 +1298,9 @@ static bool target_should_be_paused(struct ceph_osd_client *osdc,
> > > __pool_full(pi);
> > >
> > > WARN_ON(pi->id != t->base_oloc.pool);
> > > - return (t->flags & CEPH_OSD_FLAG_READ && pauserd) ||
> > > - (t->flags & CEPH_OSD_FLAG_WRITE && pausewr);
> > > + return ((t->flags & CEPH_OSD_FLAG_READ) && pauserd) ||
> > > + ((t->flags & CEPH_OSD_FLAG_WRITE) && pausewr) ||
> > > + (osdc->osdmap->epoch < osdc->epoch_barrier);
> > > }
> > >
> > > enum calc_target_result {
> > > @@ -1654,8 +1655,13 @@ static void __submit_request(struct ceph_osd_request *req, bool wrlocked)
> > > goto promote;
> > > }
> > >
> > > - if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
> > > - ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
> > > + if (osdc->osdmap->epoch < osdc->epoch_barrier) {
> > > + dout("req %p epoch %u barrier %u\n", req, osdc->osdmap->epoch,
> > > + osdc->epoch_barrier);
> > > + req->r_t.paused = true;
> > > + maybe_request_map(osdc);
> > > + } else if ((req->r_flags & CEPH_OSD_FLAG_WRITE) &&
> > > + ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
> > > dout("req %p pausewr\n", req);
> > > req->r_t.paused = true;
> > > maybe_request_map(osdc);
> > > @@ -1809,17 +1815,48 @@ static void abort_request(struct ceph_osd_request *req, int err)
> > >
> > > /*
> > > * Drop all pending requests that are stalled waiting on a full condition to
> > > - * clear, and complete them with ENOSPC as the return code.
> > > + * clear, and complete them with ENOSPC as the return code. Set the
> > > + * osdc->epoch_barrier to the latest map epoch that we've seen if any were
> > > + * cancelled.
> > > */
> > > static void ceph_osdc_abort_on_full(struct ceph_osd_client *osdc)
> > > {
> > > struct rb_node *n;
> > > + bool victims = false;
> > >
> > > dout("enter abort_on_full\n");
> > >
> > > if (!ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) && !have_pool_full(osdc))
> > > goto out;
> > >
> > > + /* Scan list and see if there is anything to abort */
> > > + for (n = rb_first(&osdc->osds); n; n = rb_next(n)) {
> > > + struct ceph_osd *osd = rb_entry(n, struct ceph_osd, o_node);
> > > + struct rb_node *m;
> > > +
> > > + m = rb_first(&osd->o_requests);
> > > + while (m) {
> > > + struct ceph_osd_request *req = rb_entry(m,
> > > + struct ceph_osd_request, r_node);
> > > + m = rb_next(m);
> > > +
> > > + if (req->r_abort_on_full) {
> > > + victims = true;
> > > + break;
> > > + }
> > > + }
> > > + if (victims)
> > > + break;
> > > + }
> > > +
> > > + if (!victims)
> > > + goto out;
> > > +
> > > + /*
> > > + * Update the barrier to current epoch since we know we have some
> > > + * calls to be aborted in the tree.
> > > + */
> > > + osdc->epoch_barrier = osdc->osdmap->epoch;
> >
> > Erm...now that I think about it even more...
> >
> > Is it possible we can end up with the eb going backward here? Suppose
> > we get a MDS cap message with a later epoch barrier, and then a map
> > update that is not quite to the barrier yet.
> >
> > I think we probably want to only set it if it's newer than what's
> > there. So this should probably read something like:
> >
> > if (osdc->osdmap->epoch > osdc->epoch_barrier)
> > osdc->epoch_barrier = osdc->osdmap->epoch;
> >
> > If no one objects, I'll go ahead and make this change in the testing
> > branch without a full re-post to the list.
>
> I'd wrap
>
> if (likely(eb > osdc->epoch_barrier)) {
> dout("updating epoch_barrier from %u to %u\n",
> osdc->epoch_barrier, eb);
> osdc->epoch_barrier = eb;
> /* Request map if we're not to the barrier yet */
> if (eb > osdc->osdmap->epoch)
> maybe_request_map(osdc);
> }
>
> from ceph_osdc_update_epoch_barrier() into update_epoch_barrier() and
> call it from here.
>
Done. Take a look at the patch in testing branch when you get a chance
and let me know if you see anything wrong there?
Thanks,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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