On Wed, Mar 29, 2017 at 1:54 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Tue, 2017-03-28 at 16:54 +0200, Ilya Dryomov wrote:
>> On Sat, Feb 25, 2017 at 6:43 PM, Jeff Layton <jlayton@xxxxxxxxxx> 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 end up cancelling requests because of a new map showing a full OSD
>> > or pool condition, then set the barrier higher than the highest replay
>> > epoch of all the cancelled requests.
>> >
>> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
>> > ---
>> > include/linux/ceph/osd_client.h | 2 ++
>> > net/ceph/osd_client.c | 51 +++++++++++++++++++++++++++++++++--------
>> > 2 files changed, 43 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
>> > index 55dcff2455e0..833942226560 100644
>> > --- a/include/linux/ceph/osd_client.h
>> > +++ b/include/linux/ceph/osd_client.h
>> > @@ -266,6 +266,7 @@ struct ceph_osd_client {
>> > struct rb_root osds; /* osds */
>> > struct list_head osd_lru; /* idle osds */
>> > spinlock_t osd_lru_lock;
>> > + u32 epoch_barrier;
>>
>> It would be good to include it in debugfs -- osdmap_show().
>>
>
> Ok, I'll plan to add it in there.
>
>> > struct ceph_osd homeless_osd;
>> > atomic64_t last_tid; /* tid of last request */
>> > u64 last_linger_id;
>> > @@ -304,6 +305,7 @@ 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/osd_client.c b/net/ceph/osd_client.c
>> > index b286ff6dec29..2e9b6211814a 100644
>> > --- a/net/ceph/osd_client.c
>> > +++ b/net/ceph/osd_client.c
>> > @@ -1299,8 +1299,10 @@ 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->epoch_barrier &&
>> > + osdc->osdmap->epoch < osdc->epoch_barrier);
>>
>> Why the osdc->epoch_barrier != 0 check, here and everywhere else?
>>
>
> My understanding is that we have to deal with clusters that predate the
> addition of this value. The client sets this to 0 when it's not set.
That and initialization to 0 in ceph_create_client(), so how does this
!= 0 check affect anything? Won't we always return false in that case,
thus preserving the old behavior?
>
>> > }
>> >
>> > enum calc_target_result {
>> > @@ -1610,21 +1612,24 @@ static void send_request(struct ceph_osd_request *req)
>> > static void maybe_request_map(struct ceph_osd_client *osdc)
>> > {
>> > bool continuous = false;
>> > + u32 epoch = osdc->osdmap->epoch;
>> >
>> > verify_osdc_locked(osdc);
>> > - WARN_ON(!osdc->osdmap->epoch);
>> > + WARN_ON_ONCE(epoch == 0);
>> >
>> > if (ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) ||
>> > ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSERD) ||
>> > - ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR)) {
>> > + ceph_osdmap_flag(osdc, CEPH_OSDMAP_PAUSEWR) ||
>> > + (osdc->epoch_barrier && epoch < osdc->epoch_barrier)) {
>> > dout("%s osdc %p continuous\n", __func__, osdc);
>> > continuous = true;
>> > } else {
>> > dout("%s osdc %p onetime\n", __func__, osdc);
>> > }
>> >
>> > + ++epoch;
>> > if (ceph_monc_want_map(&osdc->client->monc, CEPH_SUB_OSDMAP,
>> > - osdc->osdmap->epoch + 1, continuous))
>> > + epoch, continuous))
>> > ceph_monc_renew_subs(&osdc->client->monc);
>> > }
>>
>> Why was this change needed? Wouldn't the existing call to unmodified
>> maybe_request_map() from ceph_osdc_handle_map() be sufficient?
>>
>
> It's not strictly required, but it's more efficient to fetch the epoch
> at the beginning of the function like this and then work with it the
> value on the stack than to potentially deal with having to refetch it.
> It also looks cleaner.
It was more about the if condition change. I don't see a reason for it
and it's not present in the Objecter counterpart, so I'd rather we drop
the entire hunk.
Thanks,
Ilya
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