Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934042AbbFPJai (ORCPT ); Tue, 16 Jun 2015 05:30:38 -0400 Received: from mail.kernel.org ([198.145.29.136]:54727 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932352AbbFPImN (ORCPT ); Tue, 16 Jun 2015 04:42:13 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Darrick J. Wong" , Mike Snitzer , Zefan Li Subject: [PATCH 3.4 038/172] dm io: reject unsupported DISCARD requests with EOPNOTSUPP Date: Tue, 16 Jun 2015 16:34:52 +0800 Message-Id: <1434443826-4929-38-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2646 Lines: 71 From: "Darrick J. Wong" 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 37527b869207ad4c208b1e13967d69b8bba1fbf9 upstream. I created a dm-raid1 device backed by a device that supports DISCARD and another device that does NOT support DISCARD with the following dm configuration: # echo '0 2048 mirror core 1 512 2 /dev/sda 0 /dev/sdb 0' | dmsetup create moo # lsblk -D NAME DISC-ALN DISC-GRAN DISC-MAX DISC-ZERO sda 0 4K 1G 0 `-moo (dm-0) 0 4K 1G 0 sdb 0 0B 0B 0 `-moo (dm-0) 0 4K 1G 0 Notice that the mirror device /dev/mapper/moo advertises DISCARD support even though one of the mirror halves doesn't. If I issue a DISCARD request (via fstrim, mount -o discard, or ioctl BLKDISCARD) through the mirror, kmirrord gets stuck in an infinite loop in do_region() when it tries to issue a DISCARD request to sdb. The problem is that when we call do_region() against sdb, num_sectors is set to zero because q->limits.max_discard_sectors is zero. Therefore, "remaining" never decreases and the loop never terminates. To fix this: before entering the loop, check for the combination of REQ_DISCARD and no discard and return -EOPNOTSUPP to avoid hanging up the mirror device. This bug was found by the unfortunate coincidence of pvmove and a discard operation in the RHEL 6.5 kernel; upstream is also affected. Signed-off-by: Darrick J. Wong Acked-by: "Martin K. Petersen" Signed-off-by: Mike Snitzer Signed-off-by: Zefan Li --- drivers/md/dm-io.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c index ea5dd28..d3b1b54 100644 --- a/drivers/md/dm-io.c +++ b/drivers/md/dm-io.c @@ -299,6 +299,12 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where, struct request_queue *q = bdev_get_queue(where->bdev); sector_t discard_sectors; + /* Reject unsupported discard requests */ + if ((rw & REQ_DISCARD) && !blk_queue_discard(q)) { + dec_count(io, region, -EOPNOTSUPP); + return; + } + /* * where->count may be zero if rw holds a flush and we need to * send a zero-sized flush. -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/