From patchwork Thu Mar 6 08:41:50 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming-Hung Tsai X-Patchwork-Id: 14003994 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 96C8F207DE2 for ; Thu, 6 Mar 2025 08:42:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741250538; cv=none; b=WR9AAmjPDwwkOlq6T4Y5+RccejREVBaNZ70AW2jEmbv0WyVecrhsC0E5RxMuQvh4hPR5NnBb6JDt8WUAl56LOPDHcHbci+QHd4Zza0Vc2IPKu+8XJJErhpalQvAUxI7j9r9aYb+DBEdhkBfVUjncLD6VtTufPl3nlhq3lJRDgcg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741250538; c=relaxed/simple; bh=movOdMLVk1g2ahfGdAn0oI/QZx5w0fU7w79vlhTPiFs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=hVv2EpYCoTOFNi4dRr/uJQTyY3t2KFtY3ldGE1fPcAlCT+HaZg5Wydps64R7jQATCGbjLLsxlrUF3a1jTvYj9Npn+MzztciARS1EeiZXAuAUm7SskPfFfn/9DbWYDiHJQuV857KMFtBGh604mIC3dzcyVcygrG29YSu8Km2ZcH4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=dNjuQFG3; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="dNjuQFG3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741250535; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ivBZHnz6Qi50odKEW+nseJ8kl+/UWUd1Tx7nCqI/tqs=; b=dNjuQFG3ovNygymk9m14yZC6o4xpgKdyBM8uCNutUsYg+tsQRJAm7/V++4VZW6WG1oCPUK xn0lo0jY2+e2O2mMX27CQpa73MTW/UndvpNnH7oBOyBJtG6j29y5Px/BHFN9HrxLZPZX6d sDKRcxUPDWkJQokQqb3KHCX34x/bX7k= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-550-7SLr-3tPO1mgMLAUB6Zw4w-1; Thu, 06 Mar 2025 03:42:13 -0500 X-MC-Unique: 7SLr-3tPO1mgMLAUB6Zw4w-1 X-Mimecast-MFC-AGG-ID: 7SLr-3tPO1mgMLAUB6Zw4w_1741250533 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C911E1955DCD; Thu, 6 Mar 2025 08:42:12 +0000 (UTC) Received: from thinkpad.redhat.com (unknown [10.67.24.24]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 372BB300070B; Thu, 6 Mar 2025 08:42:08 +0000 (UTC) From: Ming-Hung Tsai To: dm-devel@lists.linux.dev Cc: Mikulas Patocka , Joe Thornber , Heinz Mauelshagen , Mike Snitzer , Ming-Hung Tsai Subject: [PATCH v3 1/2] dm cache: prevent BUG_ON by blocking retries on failed device resumes Date: Thu, 6 Mar 2025 16:41:50 +0800 Message-ID: <20250306084151.371591-2-mtsai@redhat.com> In-Reply-To: <20250306084151.371591-1-mtsai@redhat.com> References: <20250306084151.371591-1-mtsai@redhat.com> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: N2Lnfg0lfaM9uk3l2vuTsvVC0gu1yHX7co2IQFETDHA_1741250533 X-Mimecast-Originator: redhat.com content-type: text/plain; charset="US-ASCII"; x-default=true 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 --- 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 9cb797a561d6..6cee5eac8b9e 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -2899,6 +2899,27 @@ 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)) { @@ -2947,6 +2968,9 @@ 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. */