From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A49FB2EDB28; Mon, 5 May 2025 23:09:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486555; cv=none; b=Z/IWLKtbOerls+aJg1SVOil94M+4tsSqzaSw33LdpXhZgLXgdXIGOPbNLEUXrZfiNKwG62fV73ojxBAB9TGUqq3i4V88mo5AnQrHSwty8cDfLr9Gyqjkig+VoWtfKtsW9l/0B77zyMYq5r4b9Y80oHoBnCi2GGWEin6lgw1+Xpc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746486555; c=relaxed/simple; bh=Wv0PuBRqn/JHUW9ehWz1ZK9rxfmTdcrlgN08tUOQC+o=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=IBjJ6OJsJCPNZR0QF1q1dOb0ASzz1rraVaFMrIoCWogYnLnz+GlCMB9MmsYGfFqJbGMqCnS2wiwPybxfEiiWmoTiPovqcvBOgmUVNprDIU/rPUTUBL9eB58z6f8jqMw26S7CTUaiJLh7w/pGv7waewgVac3v3bKUIHctDrgWkvo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V79kUgy6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="V79kUgy6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99D58C4CEED; Mon, 5 May 2025 23:09:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746486554; bh=Wv0PuBRqn/JHUW9ehWz1ZK9rxfmTdcrlgN08tUOQC+o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V79kUgy6xhxaAfSulnW7lG2yOfYVmYg9TrPPrQ4KVhpQMyiYs24NNme9NTvAy0bOA nbbQfNc0P8yIdEgqrMrBMV3khiILPkYE6gFCiROIvHX6OsiI4gPyvz9YSxh/ML5eAt Cfo1pIvagTigUs7l0xknp8jubLDC1bJxltb1g5MD/rPEEp0LWMgyVSw/zRW2458lLc YMSR1NHor/MxL3KIlSQA4+4yCtvs6lbox97lbmxZ2LC4nfrZHy4yrVcd2QDXPqzgkB dhpfBujPaiTIXkUzj7KIBTrvblaEAsZ2RLlCix5K274brtKsjo7z6k86pRJa9H4pXG Xe28G9+T+nxHg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ming-Hung Tsai , Mikulas Patocka , Sasha Levin , agk@redhat.com, snitzer@kernel.org, dm-devel@lists.linux.dev Subject: [PATCH AUTOSEL 6.1 088/212] dm cache: prevent BUG_ON by blocking retries on failed device resumes Date: Mon, 5 May 2025 19:04:20 -0400 Message-Id: <20250505230624.2692522-88-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250505230624.2692522-1-sashal@kernel.org> References: <20250505230624.2692522-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.136 Content-Transfer-Encoding: 8bit From: Ming-Hung Tsai [ Upstream commit 5da692e2262b8f81993baa9592f57d12c2703dea ] A cache device failing to resume due to mapping errors should not be retried, as the failure leaves a partially initialized policy object. Repeating the resume operation risks triggering BUG_ON when reloading cache mappings into the incomplete policy object. Reproduce steps: 1. create a cache metadata consisting of 512 or more cache blocks, with some mappings stored in the first array block of the mapping array. Here we use cache_restore v1.0 to build the metadata. cat <> cmeta.xml EOF dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2 dmsetup remove cmeta 2. wipe the second array block of the mapping array to simulate data degradations. mapping_root=$(dd if=/dev/sdc bs=1c count=8 skip=192 \ 2>/dev/null | hexdump -e '1/8 "%u\n"') ablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) \ 2>/dev/null | hexdump -e '1/8 "%u\n"') dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock 3. try bringing up the cache device. The resume is expected to fail due to the broken array block. dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc 262144" dmsetup create cache --notable dmsetup load cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" dmsetup resume cache 4. try resuming the cache again. An unexpected BUG_ON is triggered while loading cache mappings. dmsetup resume cache Kernel logs: (snip) ------------[ cut here ]------------ kernel BUG at drivers/md/dm-cache-policy-smq.c:752! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 UID: 0 PID: 332 Comm: dmsetup Not tainted 6.13.4 #3 RIP: 0010:smq_load_mapping+0x3e5/0x570 Fix by disallowing resume operations for devices that failed the initial attempt. Signed-off-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka Signed-off-by: Sasha Levin --- drivers/md/dm-cache-target.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index e714114d495a9..66608b42ee1ad 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2875,6 +2875,27 @@ static dm_cblock_t get_cache_dev_size(struct cache *cache) return to_cblock(size); } +static bool can_resume(struct cache *cache) +{ + /* + * Disallow retrying the resume operation for devices that failed the + * first resume attempt, as the failure leaves the policy object partially + * initialized. Retrying could trigger BUG_ON when loading cache mappings + * into the incomplete policy object. + */ + if (cache->sized && !cache->loaded_mappings) { + if (get_cache_mode(cache) != CM_WRITE) + DMERR("%s: unable to resume a failed-loaded cache, please check metadata.", + cache_device_name(cache)); + else + DMERR("%s: unable to resume cache due to missing proper cache table reload", + cache_device_name(cache)); + return false; + } + + return true; +} + static bool can_resize(struct cache *cache, dm_cblock_t new_size) { if (from_cblock(new_size) > from_cblock(cache->cache_size)) { @@ -2923,6 +2944,9 @@ static int cache_preresume(struct dm_target *ti) struct cache *cache = ti->private; dm_cblock_t csize = get_cache_dev_size(cache); + if (!can_resume(cache)) + return -EINVAL; + /* * Check to see if the cache has resized. */ -- 2.39.5