From patchwork Tue Apr 8 20:42:45 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josh Durgin X-Patchwork-Id: 3951291 Return-Path: X-Original-To: patchwork-ceph-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 4C82ABFF02 for ; Tue, 8 Apr 2014 22:02:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4A2822025B for ; Tue, 8 Apr 2014 22:02:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 104DE204D3 for ; Tue, 8 Apr 2014 22:02:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757486AbaDHWC0 (ORCPT ); Tue, 8 Apr 2014 18:02:26 -0400 Received: from mail.hq.newdream.net ([66.33.206.127]:56374 "EHLO mail.hq.newdream.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756598AbaDHWCY (ORCPT ); Tue, 8 Apr 2014 18:02:24 -0400 Received: from mail.hq.newdream.net (localhost [127.0.0.1]) by mail.hq.newdream.net (Postfix) with ESMTP id 87FE5267D6 for ; Tue, 8 Apr 2014 14:52:31 -0700 (PDT) Received: from vit.ops.newdream.net (unknown [38.122.20.226]) by mail.hq.newdream.net (Postfix) with ESMTPSA id 7AF0D267BC for ; Tue, 8 Apr 2014 14:52:31 -0700 (PDT) From: Josh Durgin To: ceph-devel@vger.kernel.org Subject: [PATCH 01/11] rbd: access snapshot context and mapping size safely Date: Tue, 8 Apr 2014 13:42:45 -0700 Message-Id: <6db75c6e7fb22b00b3ca78ef4f4fd12e6aecdeaa.1396987789.git.josh.durgin@inktank.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: References: In-Reply-To: References: Sender: ceph-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org X-Spam-Status: No, score=-7.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP These fields may both change while the image is mapped if a snapshot is created or deleted or the image is resized. They are guarded by rbd_dev->header_rwsem, so hold that while reading them, and store a local copy to refer to outside of the critical section. The local copy will stay consistent since the snapshot context is reference counted, and the mapping size is just a u64. This prevents torn loads from giving us inconsistent values. Move reading header.snapc into the caller of rbd_img_request_create() so that we only need to take the semaphore once. The read-only caller, rbd_parent_request_create() can just pass NULL for snapc, since the snapshot context is only relevant for writes. Signed-off-by: Josh Durgin --- drivers/block/rbd.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 4c95b50..b6676b6 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -1961,7 +1961,8 @@ static bool rbd_dev_parent_get(struct rbd_device *rbd_dev) static struct rbd_img_request *rbd_img_request_create( struct rbd_device *rbd_dev, u64 offset, u64 length, - bool write_request) + bool write_request, + struct ceph_snap_context *snapc) { struct rbd_img_request *img_request; @@ -1969,12 +1970,6 @@ static struct rbd_img_request *rbd_img_request_create( if (!img_request) return NULL; - if (write_request) { - down_read(&rbd_dev->header_rwsem); - ceph_get_snap_context(rbd_dev->header.snapc); - up_read(&rbd_dev->header_rwsem); - } - img_request->rq = NULL; img_request->rbd_dev = rbd_dev; img_request->offset = offset; @@ -1982,7 +1977,7 @@ static struct rbd_img_request *rbd_img_request_create( img_request->flags = 0; if (write_request) { img_request_write_set(img_request); - img_request->snapc = rbd_dev->header.snapc; + img_request->snapc = snapc; } else { img_request->snap_id = rbd_dev->spec->snap_id; } @@ -2038,8 +2033,8 @@ static struct rbd_img_request *rbd_parent_request_create( rbd_assert(obj_request->img_request); rbd_dev = obj_request->img_request->rbd_dev; - parent_request = rbd_img_request_create(rbd_dev->parent, - img_offset, length, false); + parent_request = rbd_img_request_create(rbd_dev->parent, img_offset, + length, false, NULL); if (!parent_request) return NULL; @@ -3065,8 +3060,10 @@ static void rbd_request_fn(struct request_queue *q) while ((rq = blk_fetch_request(q))) { bool write_request = rq_data_dir(rq) == WRITE; struct rbd_img_request *img_request; + struct ceph_snap_context *snapc = NULL; u64 offset; u64 length; + u64 mapping_size; /* Ignore any non-FS requests that filter through. */ @@ -3120,8 +3117,16 @@ static void rbd_request_fn(struct request_queue *q) goto end_request; /* Shouldn't happen */ } + down_read(&rbd_dev->header_rwsem); + mapping_size = rbd_dev->mapping.size; + if (op_type != OBJ_OP_READ) { + snapc = rbd_dev->header.snapc; + ceph_get_snap_context(snapc); + } + up_read(&rbd_dev->header_rwsem); + result = -EIO; - if (offset + length > rbd_dev->mapping.size) { + if (offset + length > mapping_size) { rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)\n", offset, length, rbd_dev->mapping.size); goto end_request; @@ -3129,7 +3134,7 @@ static void rbd_request_fn(struct request_queue *q) result = -ENOMEM; img_request = rbd_img_request_create(rbd_dev, offset, length, - write_request); + write_request, snapc); if (!img_request) goto end_request; @@ -3147,6 +3152,8 @@ end_request: rbd_warn(rbd_dev, "%s %llx at %llx result %d\n", write_request ? "write" : "read", length, offset, result); + if (snapc) + ceph_put_snap_context(snapc); __blk_end_request_all(rq, result); }