Re: [PATCH v4 2/6] libceph: abort already submitted but abortable requests when map or pool goes full

[Jeff Layton <jlayton@redhat.com>]

On Fri, 2017-02-10 at 20:01 +0800, Yan, Zheng wrote:
> > On 9 Feb 2017, at 22:48, Jeff Layton <jlayton@redhat.com> wrote:
> > 
> > When a Ceph volume hits capacity, a flag is set in the OSD map to
> > indicate that, and a new map is sprayed around the cluster. With cephfs
> > we want it to shut down any abortable requests that are in progress with
> > an -ENOSPC error as they'd just hang otherwise.
> > 
> > Add a new ceph_osdc_abort_on_full helper function to handle this. It
> > will first check whether there is an out-of-space condition in the
> > cluster. It will then walk the tree and abort any request that has
> > r_abort_on_full set with an ENOSPC error. Call this new function
> > directly whenever we get a new OSD map.
> > 
> > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > ---
> > net/ceph/osd_client.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 42 insertions(+)
> > 
> > diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> > index f68bb42da240..cdb0b58c4c99 100644
> > --- a/net/ceph/osd_client.c
> > +++ b/net/ceph/osd_client.c
> > @@ -1777,6 +1777,47 @@ static void complete_request(struct ceph_osd_request *req, int err)
> > 	ceph_osdc_put_request(req);
> > }
> > 
> > +/*
> > + * Drop all pending requests that are stalled waiting on a full condition to
> > + * clear, and complete them with ENOSPC as the return code.
> > + */
> > +static void ceph_osdc_abort_on_full(struct ceph_osd_client *osdc)
> > +{
> > +	struct ceph_osd_request *req;
> > +	struct ceph_osd *osd;
> > +	struct rb_node *m, *n;
> > +	u32 latest_epoch = 0;
> > +	bool osdmap_full = ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL);
> > +
> > +	dout("enter abort_on_full\n");
> > +
> > +	if (!osdmap_full && !have_pool_full(osdc))
> > +		goto out;
> > +
> > +	for (n = rb_first(&osdc->osds); n; n = rb_next(n)) {
> > +		osd = rb_entry(n, struct ceph_osd, o_node);
> > +		mutex_lock(&osd->lock);
> > +		m = rb_first(&osd->o_requests);
> > +		while (m) {
> > +			req = rb_entry(m, struct ceph_osd_request, r_node);
> > +			m = rb_next(m);
> > +
> 
> For requests that have already got unsafe reply, we should ignore them or call req->r_unsafe_callback() to clean them up
> 
> 
> Regards
> Yan, Zheng 

Ok, yeah. I had to stare at the r_unsafe_callback code a bit the other
day to handle the ERROR_WRITE flag and what you say makes sense.

Honestly what we really need is a function like complete_request that
hides all of these fiddly details about the request state. Maybe it
would be simpler to just have complete_request handle the case where
we've gotten an unsafe reply as well?

I'll see what I can come up with there.

> > +			if (req->r_abort_on_full &&
> > +			    (osdmap_full || pool_full(osdc, req->r_t.base_oloc.pool))) {
> > +				u32 cur_epoch = le32_to_cpu(req->r_replay_version.epoch);
> > +
> > +				dout("%s: abort tid=%llu flags 0x%x\n", __func__, req->r_tid, req->r_flags);
> > +				complete_request(req, -ENOSPC);
> > +				if (cur_epoch > latest_epoch)
> > +					latest_epoch = cur_epoch;
> > +			}
> > +		}
> > +		mutex_unlock(&osd->lock);
> > +	}
> > +out:
> > +	dout("return abort_on_full latest_epoch=%u\n", latest_epoch);
> > +}
> > +
> > static void cancel_map_check(struct ceph_osd_request *req)
> > {
> > 	struct ceph_osd_client *osdc = req->r_osdc;
> > @@ -3292,6 +3333,7 @@ void ceph_osdc_handle_map(struct ceph_osd_client *osdc, struct ceph_msg *msg)
> > 
> > 	ceph_monc_got_map(&osdc->client->monc, CEPH_SUB_OSDMAP,
> > 			  osdc->osdmap->epoch);
> > +	ceph_osdc_abort_on_full(osdc);
> > 	up_write(&osdc->lock);
> > 	wake_up_all(&osdc->client->auth_wq);
> > 	return;
> > -- 
> > 2.9.3
> > 
> 
> 

-- 
Jeff Layton <jlayton@redhat.com>