From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Layton Subject: Re: [PATCH v2 6/6] libceph: allow requests to return immediately on full conditions if caller wishes Date: Mon, 06 Feb 2017 13:30:20 -0500 Message-ID: <1486405820.18829.1.camel@redhat.com> References: <20170206132927.9219-1-jlayton@redhat.com> <20170206132927.9219-7-jlayton@redhat.com> <1486396192.2712.4.camel@redhat.com> <1486398961.2712.7.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-qt0-f179.google.com ([209.85.216.179]:33238 "EHLO mail-qt0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbdBFSaY (ORCPT ); Mon, 6 Feb 2017 13:30:24 -0500 Received: by mail-qt0-f179.google.com with SMTP id v23so113251916qtb.0 for ; Mon, 06 Feb 2017 10:30:23 -0800 (PST) In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Ilya Dryomov Cc: Ceph Development , "Yan, Zheng" , Sage Weil , John Spray On Mon, 2017-02-06 at 18:05 +0100, Ilya Dryomov wrote: > On Mon, Feb 6, 2017 at 5:36 PM, Jeff Layton wrote: > > On Mon, 2017-02-06 at 17:27 +0100, Ilya Dryomov wrote: > > > On Mon, Feb 6, 2017 at 4:49 PM, Jeff Layton wrote: > > > > On Mon, 2017-02-06 at 15:09 +0100, Ilya Dryomov wrote: > > > > > > > > [...] > > > > > > > > > > diff --git a/include/linux/ceph/rados.h b/include/linux/ceph/rados.h > > > > > > index 5c0da61cb763..def43570a85a 100644 > > > > > > --- a/include/linux/ceph/rados.h > > > > > > +++ b/include/linux/ceph/rados.h > > > > > > @@ -401,6 +401,7 @@ enum { > > > > > > CEPH_OSD_FLAG_KNOWN_REDIR = 0x400000, /* redirect bit is authoritative */ > > > > > > CEPH_OSD_FLAG_FULL_TRY = 0x800000, /* try op despite full flag */ > > > > > > CEPH_OSD_FLAG_FULL_FORCE = 0x1000000, /* force op despite full flag */ > > > > > > + CEPH_OSD_FLAG_FULL_CANCEL = 0x2000000, /* cancel operation on full flag */ > > > > > > > > > > Is this a new flag? This is the wire protocol and I don't see it in > > > > > ceph.git. > > > > > > > > > > I'll look at epoch_barrier and callback stuff later. > > > > > > > > > > Thanks, > > > > > > > > > > Ilya > > > > > > > > Here's a respun version of the last patch in the set. This should avoid > > > > adding an on the wire flag. I just added a new bool and changed the > > > > code to set and look at that to indicate the desire for an immediate > > > > error return in this case. Compiles but is otherwise untested. I'll give > > > > it a go in a bit. > > > > > > > > -----------------------------8<------------------------------ > > > > > > > > libceph: allow requests to return immediately on full > > > > conditions if caller wishes > > > > > > > > Right now, cephfs will cancel any in-flight OSD write operations when a > > > > new map comes in that shows the OSD or pool as full, but nothing > > > > prevents new requests from stalling out after that point. > > > > > > > > If the caller knows that it will want an immediate error return instead > > > > of blocking on a full or at-quota error condition then allow it to set a > > > > flag to request that behavior. Cephfs write requests will always set > > > > that flag. > > > > > > > > Signed-off-by: Jeff Layton > > > > --- > > > > fs/ceph/addr.c | 4 ++++ > > > > fs/ceph/file.c | 4 ++++ > > > > include/linux/ceph/osd_client.h | 1 + > > > > net/ceph/osd_client.c | 6 ++++++ > > > > 4 files changed, 15 insertions(+) > > > > > > > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > > > > index 4547bbf80e4f..ef9c9bae7460 100644 > > > > --- a/fs/ceph/addr.c > > > > +++ b/fs/ceph/addr.c > > > > @@ -1040,6 +1040,7 @@ static int ceph_writepages_start(struct address_space *mapping, > > > > > > > > req->r_callback = writepages_finish; > > > > req->r_inode = inode; > > > > + req->r_enospc_on_full = true; > > > > > > > > /* Format the osd request message and submit the write */ > > > > len = 0; > > > > @@ -1689,6 +1690,7 @@ int ceph_uninline_data(struct file *filp, struct page *locked_page) > > > > } > > > > > > > > req->r_mtime = inode->i_mtime; > > > > + req->r_enospc_on_full = true; > > > > err = ceph_osdc_start_request(&fsc->client->osdc, req, false); > > > > if (!err) > > > > err = ceph_osdc_wait_request(&fsc->client->osdc, req); > > > > @@ -1732,6 +1734,7 @@ int ceph_uninline_data(struct file *filp, struct page *locked_page) > > > > } > > > > > > > > req->r_mtime = inode->i_mtime; > > > > + req->r_enospc_on_full = true; > > > > err = ceph_osdc_start_request(&fsc->client->osdc, req, false); > > > > if (!err) > > > > err = ceph_osdc_wait_request(&fsc->client->osdc, req); > > > > @@ -1893,6 +1896,7 @@ static int __ceph_pool_perm_get(struct ceph_inode_info *ci, > > > > err = ceph_osdc_start_request(&fsc->client->osdc, rd_req, false); > > > > > > > > wr_req->r_mtime = ci->vfs_inode.i_mtime; > > > > + wr_req->r_enospc_on_full = true; > > > > err2 = ceph_osdc_start_request(&fsc->client->osdc, wr_req, false); > > > > > > > > if (!err) > > > > diff --git a/fs/ceph/file.c b/fs/ceph/file.c > > > > index a91a4f1fc837..eaed17f90d5f 100644 > > > > --- a/fs/ceph/file.c > > > > +++ b/fs/ceph/file.c > > > > @@ -714,6 +714,7 @@ static void ceph_aio_retry_work(struct work_struct *work) > > > > req->r_callback = ceph_aio_complete_req; > > > > req->r_inode = inode; > > > > req->r_priv = aio_req; > > > > + req->r_enospc_on_full = true; > > > > > > > > ret = ceph_osdc_start_request(req->r_osdc, req, false); > > > > out: > > > > @@ -912,6 +913,7 @@ ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter, > > > > > > > > osd_req_op_init(req, 1, CEPH_OSD_OP_STARTSYNC, 0); > > > > req->r_mtime = mtime; > > > > + req->r_enospc_on_full = true; > > > > } > > > > > > > > osd_req_op_extent_osd_data_pages(req, 0, pages, len, start, > > > > @@ -1105,6 +1107,7 @@ ceph_sync_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos, > > > > false, true); > > > > > > > > req->r_mtime = mtime; > > > > + req->r_enospc_on_full = true; > > > > ret = ceph_osdc_start_request(&fsc->client->osdc, req, false); > > > > if (!ret) > > > > ret = ceph_osdc_wait_request(&fsc->client->osdc, req); > > > > @@ -1557,6 +1560,7 @@ static int ceph_zero_partial_object(struct inode *inode, > > > > } > > > > > > > > req->r_mtime = inode->i_mtime; > > > > + req->r_enospc_on_full = true; > > > > ret = ceph_osdc_start_request(&fsc->client->osdc, req, false); > > > > if (!ret) { > > > > ret = ceph_osdc_wait_request(&fsc->client->osdc, req); > > > > diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h > > > > index 17bf1873bb01..f01e93ff03d5 100644 > > > > --- a/include/linux/ceph/osd_client.h > > > > +++ b/include/linux/ceph/osd_client.h > > > > @@ -172,6 +172,7 @@ struct ceph_osd_request { > > > > > > > > int r_result; > > > > bool r_got_reply; > > > > + bool r_enospc_on_full; /* return ENOSPC when full */ > > > > > > > > struct ceph_osd_client *r_osdc; > > > > struct kref r_kref; > > > > diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c > > > > index d61d7a79fdb3..9f40d11b3c68 100644 > > > > --- a/net/ceph/osd_client.c > > > > +++ b/net/ceph/osd_client.c > > > > @@ -50,6 +50,7 @@ static void link_linger(struct ceph_osd *osd, > > > > struct ceph_osd_linger_request *lreq); > > > > static void unlink_linger(struct ceph_osd *osd, > > > > struct ceph_osd_linger_request *lreq); > > > > +static void complete_request(struct ceph_osd_request *req, int err); > > > > > > > > #if 1 > > > > static inline bool rwsem_is_wrlocked(struct rw_semaphore *sem) > > > > @@ -1643,6 +1644,7 @@ static void __submit_request(struct ceph_osd_request *req, bool wrlocked) > > > > enum calc_target_result ct_res; > > > > bool need_send = false; > > > > bool promoted = false; > > > > + int ret = 0; > > > > > > > > WARN_ON(req->r_tid || req->r_got_reply); > > > > dout("%s req %p wrlocked %d\n", __func__, req, wrlocked); > > > > @@ -1683,6 +1685,8 @@ static void __submit_request(struct ceph_osd_request *req, bool wrlocked) > > > > pr_warn_ratelimited("FULL or reached pool quota\n"); > > > > req->r_t.paused = true; > > > > maybe_request_map(osdc); > > > > + if (req->r_enospc_on_full) > > > > + ret = -ENOSPC; > > > > } else if (!osd_homeless(osd)) { > > > > need_send = true; > > > > } else { > > > > @@ -1699,6 +1703,8 @@ static void __submit_request(struct ceph_osd_request *req, bool wrlocked) > > > > link_request(osd, req); > > > > if (need_send) > > > > send_request(req); > > > > + else if (ret) > > > > + complete_request(req, ret); > > > > > > How is this handled in the userspace client? I don't see a similar > > > check in Objecter. > > > > > > Thanks, > > > > > > Ilya > > > > It seems to be handled at a much higher layer in libcephfs. In _write(), > > for instance, we have: > > > > if (objecter->osdmap_pool_full(in->layout.pool_id)) { > > return -ENOSPC; > > } > > > > ...and there's also some EDQUOT handling a little below there as well. > > > > I don't think we can reasonably follow that model in the kernel client > > though. The way it's done in userland seems to require the big client > > mutex be held over large swaths of the code, and that's not the case in > > the kernel client (thankfully). > > All it's doing is checking a flag under a lock; the same lock is taken > in ceph_osdc_start_request(). Why would exporting > > bool ceph_osdc_pool_full(osdc, pool_id) > { > bool ret; > > down_read(&osdc->lock); > ret = ceph_osdmap_flag(osdc, CEPH_OSDMAP_FULL) || > pool_full(osdc, pool_id); > up_read(&osdc->lock); > return ret; > } > > not work? IOW why special case request handling code if you know in > advance that the request is a goner? > You can't just call that before calling submit_request because once you call up_read there, the map could have changed and the map_cb already run. At that point we can't rely on the callback cancelling the now hung request. You could call that function after ceph_osdc_start_request, but before we end up waiting on it (or whatever), but then we'd need to export complete_request as well so we could cancel it. The other downside there is that we end up with even more rwsem thrashing. We already end up taking it for write in order to submit the thing, so having to take it for read again afterward is not ideal. We could remedy that by pushing the rwsem handling up into cephfs (basically, export submit_request too), but that smells more like a layering violation to me. The full flag is part of the osdmap, so it doesn't seem wrong to have libcephfs handle it, and that's quite a bit simpler and more efficient than trying to manage that from the cephfs layer. -- Jeff Layton