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 ABB51372B58; Wed, 20 May 2026 17:24:40 +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=1779297881; cv=none; b=kGkKEUhROV/8LKz3n41INy6ENWKYsbqPmNxNKEAJRySZEtAUSppmeN1W6sryQXlAoHqvmBF3tDztXU0AJr87H2uw/nLsTuj/NFrGQSxqV3Q0s+gpCMfZ+4g3KO7Y4/WEhp75Rj0Tm4E+DDOyuRpRPINlHpjDKe7CmHYvlVfsIjM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779297881; c=relaxed/simple; bh=CDo+YTRUWNfT3HZfjlfVZ+X+JHv2z4zoXJcx95Cdilk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uD2lWC6k8kuRTs0zvty/qTnLD2/+HXGP1bQGf5iGamGwni9J619hm4c+EfI6O7oL1xpBwzY+t+y2tNBYFmqdrVdjYFiae92ga12L1OtgKZ7PqRGgsI8PMmNrEK0M74LcHa3tUtgZv54w/ldcbEiezH5GC4NQuXbhP3ryqJJ3WjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cEB0VbCn; 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="cEB0VbCn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C9991F00893; Wed, 20 May 2026 17:24:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779297880; bh=bIZ8dA62MlNoeoZGuXlM2hcoitCuuICVkSBF+x/EmYQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cEB0VbCnVItFOYuuo4I16sA3AeafKhrM8ckR4O37+6sF3uw6YU4Fk7hdV8LhvTxTu ol+aF830G9AG82r00StT6Z3fz49CjAhxDvzyjloEJG7PSCI9rRh8cBe0PI1S9CGNnp wpMYWYpnoNAIC+H4+YW1Z4qLF9m4t6XKyntmtnMk= 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 6.18 199/957] dm cache: fix write path cache coherency in passthrough mode Date: Wed, 20 May 2026 18:11:22 +0200 Message-ID: <20260520162138.863485725@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162134.554764788@linuxfoundation.org> References: <20260520162134.554764788@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-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 1296965cf94cf..69fa2f6479318 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1703,6 +1703,7 @@ 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