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 A5064EB64DB for ; Mon, 19 Jun 2023 10:41:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232018AbjFSKlN (ORCPT ); Mon, 19 Jun 2023 06:41:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229730AbjFSKkn (ORCPT ); Mon, 19 Jun 2023 06:40:43 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F03B5B3 for ; Mon, 19 Jun 2023 03:40:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8E71660B33 for ; Mon, 19 Jun 2023 10:40:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4933C433C8; Mon, 19 Jun 2023 10:40:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687171242; bh=qe51Uh+xie1MnPHX/zdQ1DrgBZaG52fL+rEGpEKdbQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=e1fDJX1aYYREzydierPU1+QkyW1tV0DySNSND5j90HIHtPtv9HrRUHJX8N5flS23I xY+EkB3jjwuG5UwN0cQTl2XUfDKNjDR/AMebm5s69WjJMPH54prkq3dFEkVzjLiHCp otXKJ72q1KAQgPS47fT6fwfwVMidZO0FB27HOrRg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ross Lagerwall , Juergen Gross , Sasha Levin Subject: [PATCH 4.19 11/49] xen/blkfront: Only check REQ_FUA for writes Date: Mon, 19 Jun 2023 12:29:49 +0200 Message-ID: <20230619102130.444341275@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230619102129.856988902@linuxfoundation.org> References: <20230619102129.856988902@linuxfoundation.org> User-Agent: quilt/0.67 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: 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