From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 5/6] rbd: use reference counting for the snap context Date: Thu, 19 Jul 2012 07:35:00 -0500 Message-ID: <5007FEF4.5060401@inktank.com> References: <5007FDEA.9010605@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-gh0-f174.google.com ([209.85.160.174]:39184 "EHLO mail-gh0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751011Ab2GSMfC (ORCPT ); Thu, 19 Jul 2012 08:35:02 -0400 Received: by mail-gh0-f174.google.com with SMTP id r11so2682359ghr.19 for ; Thu, 19 Jul 2012 05:35:01 -0700 (PDT) In-Reply-To: <5007FDEA.9010605@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: "ceph-devel@vger.kernel.org" This prevents a race between requests with a given snap context and header updates that free it. The osd client was already expecting the snap context to be reference counted, since it get()s it in ceph_osdc_build_request and put()s it when the request completes. Also remove the second down_read()/up_read() on header_rwsem in rbd_do_request, which wasn't actually preventing this race or protecting any other data. Signed-off-by: Josh Durgin Reviewed-by: Alex Elder --- drivers/block/rbd.c | 36 ++++++++++++++++++------------------ 1 files changed, 18 insertions(+), 18 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index a6bbda2..988f944 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -626,7 +626,7 @@ static void rbd_header_free(struct rbd_image_header *header) kfree(header->object_prefix); kfree(header->snap_sizes); kfree(header->snap_names); - kfree(header->snapc); + ceph_put_snap_context(header->snapc); } /* @@ -902,13 +902,10 @@ static int rbd_do_request(struct request *rq, dout("rbd_do_request object_name=%s ofs=%lld len=%lld\n", object_name, len, ofs); - down_read(&rbd_dev->header_rwsem); - osdc = &rbd_dev->rbd_client->client->osdc; req = ceph_osdc_alloc_request(osdc, flags, snapc, ops, false, GFP_NOIO, pages, bio); if (!req) { - up_read(&rbd_dev->header_rwsem); ret = -ENOMEM; goto done_pages; } @@ -942,7 +939,6 @@ static int rbd_do_request(struct request *rq, snapc, &mtime, req->r_oid, req->r_oid_len); - up_read(&rbd_dev->header_rwsem); if (linger_req) { ceph_osdc_set_request_linger(osdc, req); @@ -1448,6 +1444,7 @@ static void rbd_rq_fn(struct request_queue *q) u64 ofs; int num_segs, cur_seg = 0; struct rbd_req_coll *coll; + struct ceph_snap_context *snapc; /* peek at request from block layer */ if (!rq) @@ -1474,21 +1471,20 @@ static void rbd_rq_fn(struct request_queue *q) spin_unlock_irq(q->queue_lock); - if (rbd_dev->snap_id != CEPH_NOSNAP) { - bool snap_exists; + down_read(&rbd_dev->header_rwsem); - down_read(&rbd_dev->header_rwsem); - snap_exists = rbd_dev->snap_exists; + if (rbd_dev->snap_id != CEPH_NOSNAP && !rbd_dev->snap_exists) { up_read(&rbd_dev->header_rwsem); - - if (!snap_exists) { - dout("request for non-existent snapshot"); - spin_lock_irq(q->queue_lock); - __blk_end_request_all(rq, -ENXIO); - continue; - } + dout("request for non-existent snapshot"); + spin_lock_irq(q->queue_lock); + __blk_end_request_all(rq, -ENXIO); + continue; } + snapc = ceph_get_snap_context(rbd_dev->header.snapc); + + up_read(&rbd_dev->header_rwsem); + dout("%s 0x%x bytes at 0x%llx\n", do_write ? "write" : "read", size, blk_rq_pos(rq) * SECTOR_SIZE); @@ -1498,6 +1494,7 @@ static void rbd_rq_fn(struct request_queue *q) if (!coll) { spin_lock_irq(q->queue_lock); __blk_end_request_all(rq, -ENOMEM); + ceph_put_snap_context(snapc); continue; } @@ -1521,7 +1518,7 @@ static void rbd_rq_fn(struct request_queue *q) /* init OSD command: write or read */ if (do_write) rbd_req_write(rq, rbd_dev, - rbd_dev->header.snapc, + snapc, ofs, op_size, bio, coll, cur_seg); @@ -1544,6 +1541,8 @@ next_seg: if (bp) bio_pair_release(bp); spin_lock_irq(q->queue_lock); + + ceph_put_snap_context(snapc); } } @@ -1744,7 +1743,8 @@ static int __rbd_refresh_header(struct rbd_device *rbd_dev) /* rbd_dev->header.object_prefix shouldn't change */ kfree(rbd_dev->header.snap_sizes); kfree(rbd_dev->header.snap_names); - kfree(rbd_dev->header.snapc); + /* osd requests may still refer to snapc */ + ceph_put_snap_context(rbd_dev->header.snapc); rbd_dev->header.image_size = h.image_size; rbd_dev->header.total_snaps = h.total_snaps; -- 1.7.5.4