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 7D044C77B7A for ; Wed, 31 May 2023 13:43:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235918AbjEaNnb (ORCPT ); Wed, 31 May 2023 09:43:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55150 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236490AbjEaNmi (ORCPT ); Wed, 31 May 2023 09:42:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDC541725; Wed, 31 May 2023 06:41:45 -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 9C7E363B2A; Wed, 31 May 2023 13:41:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12D34C4339E; Wed, 31 May 2023 13:41:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685540505; bh=HlwpPDD095eWKjo4oiJTfkTblpFKG89ZfJEGh62GyPQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I/AHXEi4gffcFw4H66NjLeAgQNUYA65+rfeyDw9g9EI9otB/vWnYXMywDCAPJM6mC 5tZlSW4po/mbyAXem2lAlTLjPpUODxdi1rvb2HIJ9ceHBoIQMao9wimysTy4If9eQO O4JS4pa+Upf8wMKAibsOJiitfK++uSS6s6ZbcS8l9+6CdnKx2r0o3+6/c9/s8XR+1r /WxTGS0PKR3e3Q5uJ57QQpWrStjhjeXT41+URM/KxRmAmg8QGbGJajaTF6O93pT4EQ jSHyodjTI48Rr2cR1Z6pBOtecZf13LElNc5IsWyF7Rdne/II5CXCweCYO3cC0dlsIC GBAamB3O5GgPA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ross Lagerwall , Juergen Gross , Sasha Levin , sstabellini@kernel.org, roger.pau@citrix.com, axboe@kernel.dk, xen-devel@lists.xenproject.org, linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 6.3 34/37] xen/blkfront: Only check REQ_FUA for writes Date: Wed, 31 May 2023 09:40:16 -0400 Message-Id: <20230531134020.3383253-34-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230531134020.3383253-1-sashal@kernel.org> References: <20230531134020.3383253-1-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 23ed258b57f0e..c1890c8a9f6e7 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -780,7 +780,8 @@ 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