From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kiyoshi Ueda Subject: [PATCH 3/8] dm core: reject I/O violating new queue limits Date: Wed, 18 Mar 2009 17:53:09 +0900 Message-ID: <49C0B675.6000905@ct.jp.nec.com> References: <49C0B474.4000204@ct.jp.nec.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49C0B474.4000204@ct.jp.nec.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Alasdair Kergon Cc: Christof Schmitt , device-mapper development List-Id: dm-devel.ids This patch detects requests violating the queue limitations and rejects them. The same limitation checks are done when requests are submitted to the queue by blk_insert_cloned_request(). However, such violation can happen if a table is swapped and the queue limitations are shrunk while some requests are in the queue. Since struct request is a reliable one in the block layer and device drivers, dispatching such requests is pretty dangerous. (e.g. it may cause kernel panic easily.) So avoid to dispatch such problematic requests in request-based dm. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Cc: Alasdair G Kergon --- drivers/md/dm.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) Index: 2.6.29-rc8/drivers/md/dm.c =================================================================== --- 2.6.29-rc8.orig/drivers/md/dm.c +++ 2.6.29-rc8/drivers/md/dm.c @@ -1492,6 +1492,30 @@ static void map_request(struct dm_target dm_get(md); tio->ti = ti; + + /* + * Although submitted requests to the md->queue are checked against + * the table/queue limitations at the submission time, the limitations + * may be changed by a table swapping while those already checked + * requests are in the md->queue. + * If the limitations have been shrunk in such situations, we may be + * dispatching requests violating the current limitations here. + * Since struct request is a reliable one in the block-layer + * and device drivers, dispatching such requests is dangerous. + * (e.g. it may cause kernel panic easily.) + * Avoid to dispatch such problematic requests in request-based dm. + * + * Since dm_kill_unmapped_request() expects that tio->ti is correctly + * set, this has to be done after the set. + */ + r = blk_rq_check_limits(rq->q, rq); + if (unlikely(r)) { + DMWARN("violating the queue limitation. the limitation may be" + " shrunk while there are some requests in the queue."); + dm_kill_unmapped_request(clone, r); + return; + } + r = ti->type->map_rq(ti, clone, &tio->info); switch (r) { case DM_MAPIO_SUBMITTED: