LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
To: jens.axboe@oracle.com, agk@redhat.com,
	James.Bottomley@HansenPartnership.com
Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
	dm-devel@redhat.com, j-nomura@ce.jp.nec.com,
	k-ueda@ct.jp.nec.com
Subject: [PATCH 12/13] dm: reject I/O violating new queue limits
Date: Fri, 12 Sep 2008 10:46:58 -0400 (EDT)	[thread overview]
Message-ID: <20080912.104658.89041290.k-ueda@ct.jp.nec.com> (raw)
In-Reply-To: <20080912.103814.74754581.k-ueda@ct.jp.nec.com>

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_submit_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 <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Alasdair G Kergon <agk@redhat.com>
---
 drivers/md/dm.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+)

Index: 2.6.27-rc6/drivers/md/dm.c
===================================================================
--- 2.6.27-rc6.orig/drivers/md/dm.c
+++ 2.6.27-rc6/drivers/md/dm.c
@@ -1469,6 +1469,30 @@ static void map_request(struct dm_target
 
 	tio->ti = ti;
 	atomic_inc(&md->pending);
+
+	/*
+	 * 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_request() decrements the md->pending, this have to
+	 * be done after incrementing the md->pending.
+	 */
+	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_request(clone, r);
+		return;
+	}
+
 	r = ti->type->map_rq(ti, clone, &tio->info);
 	switch (r) {
 	case DM_MAPIO_SUBMITTED:

  parent reply	other threads:[~2008-09-12 14:46 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-09-12 14:38 [PATCH 00/13] request-based dm-multipath Kiyoshi Ueda
2008-09-12 14:40 ` [PATCH 01/13] block: add request update interface Kiyoshi Ueda
2008-09-12 14:41 ` [PATCH 02/13] block: add request submission interface Kiyoshi Ueda
2008-09-14 13:10   ` Boaz Harrosh
2008-09-16 16:06     ` Kiyoshi Ueda
2008-09-16 17:02       ` Jens Axboe
2008-09-16 18:12         ` Kiyoshi Ueda
2008-09-12 14:42 ` [PATCH 03/13] mm: lld busy status exporting interface Kiyoshi Ueda
2008-09-12 14:43 ` [PATCH 04/13] scsi: exports busy status Kiyoshi Ueda
2008-09-12 14:43 ` [PATCH 05/13] block: add a queue flag for request stacking support Kiyoshi Ueda
2008-09-12 14:44 ` [PATCH 06/13] dm: remove unused DM_WQ_FLUSH_ALL Kiyoshi Ueda
2008-09-12 14:44 ` [PATCH 07/13] dm: tidy local_init Kiyoshi Ueda
2008-09-12 14:45 ` [PATCH 08/13] dm: add kmem_cache for request-based dm Kiyoshi Ueda
2008-09-12 14:45 ` [PATCH 09/13] dm: add target interfaces " Kiyoshi Ueda
2008-09-12 14:46 ` [PATCH 10/13] dm: add core functions " Kiyoshi Ueda
2008-10-24  7:44   ` [dm-devel] " Nikanth K
2008-10-28 16:00     ` Kiyoshi Ueda
     [not found]     ` <490FB852.3FEE.00C5.1@novell.com>
     [not found]       ` <49102C03020000C50002E257@victor.provo.novell.com>
2008-11-04 15:01         ` Kiyoshi Ueda
2008-09-12 14:46 ` [PATCH 11/13] dm: enable " Kiyoshi Ueda
2008-10-24  7:52   ` [dm-devel] " Nikanth K
2008-10-28 16:02     ` Kiyoshi Ueda
2008-09-12 14:46 ` Kiyoshi Ueda [this message]
2008-09-12 14:47 ` [PATCH 13/13] dm-mpath: convert to request-based Kiyoshi Ueda
2008-10-24  7:55   ` [dm-devel] " Nikanth K
2008-10-28 16:03     ` Kiyoshi Ueda
2008-09-14 13:17 ` [PATCH 00/13] request-based dm-multipath Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080912.104658.89041290.k-ueda@ct.jp.nec.com \
    --to=k-ueda@ct.jp.nec.com \
    --cc=James.Bottomley@HansenPartnership.com \
    --cc=agk@redhat.com \
    --cc=dm-devel@redhat.com \
    --cc=j-nomura@ce.jp.nec.com \
    --cc=jens.axboe@oracle.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-scsi@vger.kernel.org \
    --subject='Re: [PATCH 12/13] dm: reject I/O violating new queue limits' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).