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 X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6457DC433E0 for ; Mon, 18 Jan 2021 11:37:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 13340229C7 for ; Mon, 18 Jan 2021 11:37:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387722AbhARLhh (ORCPT ); Mon, 18 Jan 2021 06:37:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:33414 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390149AbhARLh1 (ORCPT ); Mon, 18 Jan 2021 06:37:27 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id C5C3E22571; Mon, 18 Jan 2021 11:36:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610969777; bh=0thjbtQYsA7aykU+mLkTYnE/zohDwhWqFMB8iiAU/co=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wsv8psmXoYavfJfxTHlxJSLMQRWWrcgUcrWGEUuePsyZuvwAzcHXtpZ3ilJ9W/v3h knHjbNefB2SymhhsO/OfHJs05iADewdlqSVY6TYaJ6CUI2qRG+lvbtuvaNLaLHKZTL owMV/U1zNJitiSH/U9dH+aZjqwSJezVQlgIYTWY8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Akilesh Kailash , Mike Snitzer Subject: [PATCH 4.19 09/43] dm snapshot: flush merged data before committing metadata Date: Mon, 18 Jan 2021 12:34:32 +0100 Message-Id: <20210118113335.395586843@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210118113334.966227881@linuxfoundation.org> References: <20210118113334.966227881@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: stable@vger.kernel.org From: Akilesh Kailash commit fcc42338375a1e67b8568dbb558f8b784d0f3b01 upstream. If the origin device has a volatile write-back cache and the following events occur: 1: After finishing merge operation of one set of exceptions, merge_callback() is invoked. 2: Update the metadata in COW device tracking the merge completion. This update to COW device is flushed cleanly. 3: System crashes and the origin device's cache where the recent merge was completed has not been flushed. During the next cycle when we read the metadata from the COW device, we will skip reading those metadata whose merge was completed in step (1). This will lead to data loss/corruption. To address this, flush the origin device post merge IO before updating the metadata. Cc: stable@vger.kernel.org Signed-off-by: Akilesh Kailash Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-snap.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -137,6 +137,11 @@ struct dm_snapshot { * for them to be committed. */ struct bio_list bios_queued_during_merge; + + /* + * Flush data after merge. + */ + struct bio flush_bio; }; /* @@ -1061,6 +1066,17 @@ shut: static void error_bios(struct bio *bio); +static int flush_data(struct dm_snapshot *s) +{ + struct bio *flush_bio = &s->flush_bio; + + bio_reset(flush_bio); + bio_set_dev(flush_bio, s->origin->bdev); + flush_bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH; + + return submit_bio_wait(flush_bio); +} + static void merge_callback(int read_err, unsigned long write_err, void *context) { struct dm_snapshot *s = context; @@ -1074,6 +1090,11 @@ static void merge_callback(int read_err, goto shut; } + if (flush_data(s) < 0) { + DMERR("Flush after merge failed: shutting down merge"); + goto shut; + } + if (s->store->type->commit_merge(s->store, s->num_merging_chunks) < 0) { DMERR("Write error in exception store: shutting down merge"); @@ -1198,6 +1219,7 @@ static int snapshot_ctr(struct dm_target s->first_merging_chunk = 0; s->num_merging_chunks = 0; bio_list_init(&s->bios_queued_during_merge); + bio_init(&s->flush_bio, NULL, 0); /* Allocate hash table for COW data */ if (init_hash_tables(s)) { @@ -1391,6 +1413,8 @@ static void snapshot_dtr(struct dm_targe mutex_destroy(&s->lock); + bio_uninit(&s->flush_bio); + dm_put_device(ti, s->cow); dm_put_device(ti, s->origin);