From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2AF8623392B; Sat, 30 May 2026 18:02:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164131; cv=none; b=MbdW5WzkTO6EogLbyjLyZeKkxQEENoMsJyLMjrbbMJHJ1YAwm4SvFcN40fvV1hiG0J2Lw8YsNh2lsoj4j9eXV72Z4ezlOBBZAtlclHEwqLZWt9EXFPmkzohCMyx/bRk+X8rb2YVN+GMwND2+7c+4w2CRSdJ1wWRw7of5ZLZX8f0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164131; c=relaxed/simple; bh=Wp5XM9p+oBoFCHsXpNAWD5uuQpck8Tvu8X5crusUdKo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kNrFoV92y4GpZpE3tkQRlNMZ7pCfBdBQsgGQHkdH3kulx2OSGvTlBlonr9Abf2jO69iu2uMUqNYjtGTKgOUk5fFO6ydBvXHSZ8H/wy/rDhUOF04ncKk+FPAJXKQ5DAid41QJ6MMnlV4OYv2ar0HVtopvE6TN009DkYCsZ2JPHX4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QWXYVrWE; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="QWXYVrWE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D7671F00893; Sat, 30 May 2026 18:02:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780164130; bh=/6Qk1Dt3sdEE2/pqHu836jZycKcVzY9JAK8/cB5pGwI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=QWXYVrWEBc459DC6KzgWHMNNw/DTVc5HVsTXBM2zaFXNiHKq06qkCuoxIzLKr/5tT 5A1D2AyuV4474EIN1r+a5GlJROk+qwW4ZUXvm2e/44KejcoTINMGnY7wgEFS48Y/6x Cps3LWyLYieaoe2nKbF3jQUJLdM3+ZC/eEOIrPOw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ming-Hung Tsai , Mikulas Patocka , Sasha Levin Subject: [PATCH 5.15 434/776] dm cache: fix write path cache coherency in passthrough mode Date: Sat, 30 May 2026 18:02:28 +0200 Message-ID: <20260530160251.646912173@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming-Hung Tsai [ Upstream commit 0c5eef0aad508231d8e43ff8392692925e131b68 ] In passthrough mode, dm-cache defers write bio submission until cache invalidation completes to maintain existing coherency, requiring the target map function to return DM_MAPIO_SUBMITTED. The current map_bio() returns DM_MAPIO_REMAPPED, violating the required ordering constraint. Reproduce steps: 1. Create a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into the cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first data block, and check io ordering using ftrace echo 1 > /sys/kernel/debug/tracing/events/block/block_bio_queue/enable echo 1 > /sys/kernel/debug/tracing/events/block/block_bio_complete/enable echo 1 > /sys/kernel/debug/tracing/events/block/block_rq_complete/enable fio --filename=/dev/mapper/cache --name=test --rw=write --bs=64k \ --direct=1 --size 64k 5. ftrace logs show that write operations to the cache origin (252:2) and metadata operations (252:0) are unsynchronized: the origin write occurs before metadata commit. fio-146 [000] ..... 420.139562: block_bio_queue: 252,3 WS 0 + 128 [fio] fio-146 [000] ..... 420.149395: block_bio_queue: 252,2 WS 0 + 128 [fio] fio-146 [000] ..... 420.149763: block_bio_queue: 8,32 WS 262144 + 128 [fio] fio-146 [000] dNh1. 420.151446: block_rq_complete: 8,32 WS () 262144 + 128 be,0,4 [0] fio-146 [000] dNh1. 420.152731: block_bio_complete: 252,2 WS 0 + 128 [0] fio-146 [000] dNh1. 420.154229: block_bio_complete: 252,3 WS 0 + 128 [0] kworker/0:0-9 [000] ..... 420.160530: block_bio_queue: 252,0 W 408 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.161641: block_bio_queue: 8,32 W 408 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.162533: block_bio_queue: 252,0 W 416 + 8 [kworker/0:0] kworker/0:0-9 [000] ..... 420.162821: block_bio_queue: 8,32 W 416 + 8 [kworker/0:0] Fixes: b29d4986d0da ("dm cache: significant rework to leverage dm-bio-prison-v2") Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin --- drivers/md/dm-cache-target.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 8571c095793b5..783722a4c3364 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1684,6 +1684,7 @@ static int map_bio(struct cache *cache, struct bio *bio, dm_oblock_t block, bio_drop_shared_lock(cache, bio); atomic_inc(&cache->stats.demotion); invalidate_start(cache, cblock, block, bio); + return DM_MAPIO_SUBMITTED; } else remap_to_origin_clear_discard(cache, bio, block); } else { -- 2.53.0