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 B6AE81ED38 for ; Tue, 25 Jul 2023 11:11:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A572C433C7; Tue, 25 Jul 2023 11:11:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1690283497; bh=YczOVFZ+6g91yzuremJu1rdzZruFTsKOVjXHaoiujSg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bHMAIlnmw4UAUZEmm/5F9uqn6C19lvGlgNub+9W2Ykv20f+LUv05yY4NJmfz3sGNE 8I9uiXNFNbxEm9fRoy2Y6Hhd4UEeremLL308dxHAAdeQlNWlUsg+ruwdq5MPuOj5Ln T+oyHcr5h6c8PJ1dlWeXa3gU4hGN2OeUX5BSOop4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Li Nan , Yu Kuai , Song Liu , Sasha Levin Subject: [PATCH 5.10 019/509] md/raid10: fix io loss while replacement replace rdev Date: Tue, 25 Jul 2023 12:39:18 +0200 Message-ID: <20230725104554.526317716@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230725104553.588743331@linuxfoundation.org> References: <20230725104553.588743331@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Li Nan [ Upstream commit 2ae6aaf76912bae53c74b191569d2ab484f24bf3 ] When removing a disk with replacement, the replacement will be used to replace rdev. During this process, there is a brief window in which both rdev and replacement are read as NULL in raid10_write_request(). This will result in io not being submitted but it should be. //remove //write raid10_remove_disk raid10_write_request mirror->rdev = NULL read rdev -> NULL mirror->rdev = mirror->replacement mirror->replacement = NULL read replacement -> NULL Fix it by reading replacement first and rdev later, meanwhile, use smp_mb() to prevent memory reordering. Fixes: 475b0321a4df ("md/raid10: writes should get directed to replacement as well as original.") Signed-off-by: Li Nan Reviewed-by: Yu Kuai Signed-off-by: Song Liu Link: https://lore.kernel.org/r/20230602091839.743798-3-linan666@huaweicloud.com Signed-off-by: Sasha Levin --- drivers/md/raid10.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 01680029f0de5..32a917e5103a6 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -751,8 +751,16 @@ static struct md_rdev *read_balance(struct r10conf *conf, disk = r10_bio->devs[slot].devnum; rdev = rcu_dereference(conf->mirrors[disk].replacement); if (rdev == NULL || test_bit(Faulty, &rdev->flags) || - r10_bio->devs[slot].addr + sectors > rdev->recovery_offset) + r10_bio->devs[slot].addr + sectors > + rdev->recovery_offset) { + /* + * Read replacement first to prevent reading both rdev + * and replacement as NULL during replacement replace + * rdev. + */ + smp_mb(); rdev = rcu_dereference(conf->mirrors[disk].rdev); + } if (rdev == NULL || test_bit(Faulty, &rdev->flags)) continue; @@ -1346,9 +1354,15 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio, for (i = 0; i < conf->copies; i++) { int d = r10_bio->devs[i].devnum; - struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev); - struct md_rdev *rrdev = rcu_dereference( - conf->mirrors[d].replacement); + struct md_rdev *rdev, *rrdev; + + rrdev = rcu_dereference(conf->mirrors[d].replacement); + /* + * Read replacement first to prevent reading both rdev and + * replacement as NULL during replacement replace rdev. + */ + smp_mb(); + rdev = rcu_dereference(conf->mirrors[d].rdev); if (rdev == rrdev) rrdev = NULL; if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) { -- 2.39.2