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 D39B7C77B7A for ; Wed, 31 May 2023 13:53:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236840AbjEaNx2 (ORCPT ); Wed, 31 May 2023 09:53:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237418AbjEaNue (ORCPT ); Wed, 31 May 2023 09:50:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 414C83585; Wed, 31 May 2023 06:46:07 -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 32D3063B35; Wed, 31 May 2023 13:46:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9EE64C4339C; Wed, 31 May 2023 13:46:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685540765; bh=qe51Uh+xie1MnPHX/zdQ1DrgBZaG52fL+rEGpEKdbQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HKv9cA9JPJAJwhfbTm6jHu0QkID9eCk4IbY3AqU8Kh464GkUNJ31RD0E/0RIOcECc j5BLUQuZEDkFKalDrd01JXDO8orqQ2gaK8HjL7c2+P/B0ImJi9rpbqXGGW/Wd3rl2Q ZXJAoPnE5dsBMHHLOwaheR4mMJ7Csj17uWi7vvMvaqiJfzOQV/SlzW86zzQO6L0Ktd 87w/ck4WsEw+5N2B/CBhDzKfDyKBKWWE7NsXA/5lMIpNP4KfXqw6qHA0HU1DDIeKDc 7hW9A2GyHVLWPSTB1G/G/yKqdbPckCRN4MVG4zqT8A1fZM0Usl/TvAudp9nxuktwG2 PRmPLu8fbQFkw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ross Lagerwall , Juergen Gross , Sasha Levin , roger.pau@citrix.com, sstabellini@kernel.org, axboe@kernel.dk, xen-devel@lists.xenproject.org, linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 13/13] xen/blkfront: Only check REQ_FUA for writes Date: Wed, 31 May 2023 09:45:41 -0400 Message-Id: <20230531134541.3385043-13-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230531134541.3385043-1-sashal@kernel.org> References: <20230531134541.3385043-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ross Lagerwall [ Upstream commit b6ebaa8100090092aa602530d7e8316816d0c98d ] The existing code silently converts read operations with the REQ_FUA bit set into write-barrier operations. This results in data loss as the backend scribbles zeroes over the data instead of returning it. While the REQ_FUA bit doesn't make sense on a read operation, at least one well-known out-of-tree kernel module does set it and since it results in data loss, let's be safe here and only look at REQ_FUA for writes. Signed-off-by: Ross Lagerwall Acked-by: Juergen Gross Link: https://lore.kernel.org/r/20230426164005.2213139-1-ross.lagerwall@citrix.com Signed-off-by: Juergen Gross Signed-off-by: Sasha Levin --- drivers/block/xen-blkfront.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 7ee618ab1567b..b4807d12ef29c 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -779,7 +779,8 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri ring_req->u.rw.handle = info->handle; ring_req->operation = rq_data_dir(req) ? BLKIF_OP_WRITE : BLKIF_OP_READ; - if (req_op(req) == REQ_OP_FLUSH || req->cmd_flags & REQ_FUA) { + if (req_op(req) == REQ_OP_FLUSH || + (req_op(req) == REQ_OP_WRITE && (req->cmd_flags & REQ_FUA))) { /* * Ideally we can do an unordered flush-to-disk. * In case the backend onlysupports barriers, use that. -- 2.39.2