From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F8F4C433F5 for ; Mon, 18 Apr 2022 13:32:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242274AbiDRNfQ (ORCPT ); Mon, 18 Apr 2022 09:35:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242688AbiDRNJU (ORCPT ); Mon, 18 Apr 2022 09:09:20 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 511E636173; Mon, 18 Apr 2022 05:48:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A504061267; Mon, 18 Apr 2022 12:48:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F208C385A1; Mon, 18 Apr 2022 12:48:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650286128; bh=ppHpru4VsQzJxITMdZEUGtbM4eqf231wGeMtdnZLn78=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TmBrCtWb+uwMn+RNwBccyaM1Fsp8Z/9x2ePMJOlDS3SdNhVEJhoLxPp3MqWjoicKU Lq0zTBM9Evu7/jWnn7bYC+or5Ul2NAi+mWClVDRGNnVOrYuqsGWYSpv19rGUawG4fp CQn2c7XeR4Dqxz3kXVgtzLzbq8VXc3qbtuSaAsns= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lars Ellenberg , =?UTF-8?q?Christoph=20B=C3=B6hmwalder?= , Jens Axboe Subject: [PATCH 4.14 036/284] drbd: fix potential silent data corruption Date: Mon, 18 Apr 2022 14:10:17 +0200 Message-Id: <20220418121211.721427897@linuxfoundation.org> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220418121210.689577360@linuxfoundation.org> References: <20220418121210.689577360@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lars Ellenberg commit f4329d1f848ac35757d9cc5487669d19dfc5979c upstream. Scenario: --------- bio chain generated by blk_queue_split(). Some split bio fails and propagates its error status to the "parent" bio. But then the (last part of the) parent bio itself completes without error. We would clobber the already recorded error status with BLK_STS_OK, causing silent data corruption. Reproducer: ----------- How to trigger this in the real world within seconds: DRBD on top of degraded parity raid, small stripe_cache_size, large read_ahead setting. Drop page cache (sysctl vm.drop_caches=1, fadvise "DONTNEED", umount and mount again, "reboot"). Cause significant read ahead. Large read ahead request is split by blk_queue_split(). Parts of the read ahead that are already in the stripe cache, or find an available stripe cache to use, can be serviced. Parts of the read ahead that would need "too much work", would need to wait for a "stripe_head" to become available, are rejected immediately. For larger read ahead requests that are split in many pieces, it is very likely that some "splits" will be serviced, but then the stripe cache is exhausted/busy, and the remaining ones will be rejected. Signed-off-by: Lars Ellenberg Signed-off-by: Christoph Böhmwalder Cc: # 4.13.x Link: https://lore.kernel.org/r/20220330185551.3553196-1-christoph.boehmwalder@linbit.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/drbd/drbd_req.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/block/drbd/drbd_req.c +++ b/drivers/block/drbd/drbd_req.c @@ -207,7 +207,8 @@ void start_new_tl_epoch(struct drbd_conn void complete_master_bio(struct drbd_device *device, struct bio_and_error *m) { - m->bio->bi_status = errno_to_blk_status(m->error); + if (unlikely(m->error)) + m->bio->bi_status = errno_to_blk_status(m->error); bio_endio(m->bio); dec_ap_bio(device); }