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 5777DC7EE23 for ; Wed, 31 May 2023 13:52:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237219AbjEaNwr (ORCPT ); Wed, 31 May 2023 09:52:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237291AbjEaNuT (ORCPT ); Wed, 31 May 2023 09:50:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFAEF2D7C; Wed, 31 May 2023 06:45:47 -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 5E1A663B7F; Wed, 31 May 2023 13:45:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C77B2C4339B; Wed, 31 May 2023 13:45:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685540731; bh=p/IgxmZZFrxBdPYVbroxVgHz0FMQYuzCL/FQBFsDPeg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gsP/PpgZHs3JyUBeO4WmELP+CM81s9Hiotlsj3drW6kgRnoApYPP4gwPRoGlxiToN 2HQ/VxH88YGyziOO7f5vP2d3jGDWpc9ZyHqXnGridTKFGsiwI3RmL1oUSPhIniFVOB XW0CE3vz1QVXahSOtTRh98XWhpLruunBjXDrQytm1i/+XefEIXcnuojAxs951Cuqw3 GZJupS/PLGEAZhy4/UdY1OIQkLxxGMQYdUB+3tLgaCqyEd1aw9aK1C8mX6F3dtsEkT WpbY+g9tk43wKb7AxxI9YjQDJonXqT9opxC7z+dRHFQ2ST34LgtY43QUVpRqzATJ3L Ns6uxmx64+BRw== 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 5.4 16/17] xen/blkfront: Only check REQ_FUA for writes Date: Wed, 31 May 2023 09:45:00 -0400 Message-Id: <20230531134502.3384828-16-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230531134502.3384828-1-sashal@kernel.org> References: <20230531134502.3384828-1-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 d0538c03f0332..da67621ebc212 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