From patchwork Mon Feb 12 23:05:58 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ross Zwisler X-Patchwork-Id: 10214861 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 799E660153 for ; Mon, 12 Feb 2018 23:06:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 78A4028631 for ; Mon, 12 Feb 2018 23:06:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6BA0B28D50; Mon, 12 Feb 2018 23:06:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id CEE7928631 for ; Mon, 12 Feb 2018 23:06:18 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id A92EE22361E47; Mon, 12 Feb 2018 15:00:28 -0800 (PST) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received-SPF: None (no SPF record) identity=mailfrom; client-ip=192.55.52.88; helo=mga01.intel.com; envelope-from=ross.zwisler@linux.intel.com; receiver=linux-nvdimm@lists.01.org Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 27E0E222DE132 for ; Mon, 12 Feb 2018 15:00:26 -0800 (PST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Feb 2018 15:06:16 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,504,1511856000"; d="scan'208";a="17619324" Received: from theros.lm.intel.com ([10.232.112.164]) by orsmga008.jf.intel.com with ESMTP; 12 Feb 2018 15:06:15 -0800 From: Ross Zwisler To: linux-kernel@vger.kernel.org Subject: [PATCH] loop: Fix lost writes caused by missing flag Date: Mon, 12 Feb 2018 16:05:58 -0700 Message-Id: <20180212230558.5546-1-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.14.3 X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: stable@vger.kernel.org, Christoph Hellwig , Al Viro , linux-nvdimm@lists.01.org MIME-Version: 1.0 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Virus-Scanned: ClamAV using ClamSMTP The following commit: commit aa4d86163e4e ("block: loop: switch to VFS ITER_BVEC") replaced __do_lo_send_write(), which used ITER_KVEC iterators, with lo_write_bvec() which uses ITER_BVEC iterators. In this change, though, the WRITE flag was lost: - iov_iter_kvec(&from, ITER_KVEC | WRITE, &kvec, 1, len); + iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len); This flag is necessary for the DAX case because we make decisions based on whether or not the iterator is a READ or a WRITE in dax_iomap_actor() and in dax_iomap_rw(). We end up going through this path in configurations where we combine a PMEM device with 4k sectors, a loopback device and DAX. The consequence of this missed flag is that what we intend as a write actually turns into a read in the DAX code, so no data is ever written. The very simplest test case is to create a loopback device and try and write a small string to it, then hexdump a few bytes of the device to see if the write took. Without this patch you read back all zeros, with this you read back the string you wrote. For XFS this causes us to fail or panic during the following xfstests: xfs/074 xfs/078 xfs/216 xfs/217 xfs/250 For ext4 we have a similar issue where writes never happen, but we don't currently have any xfstests that use loopback and show this issue. Fix this by restoring the WRITE flag argument to iov_iter_bvec(). This causes the xfstests to all pass. Signed-off-by: Ross Zwisler Fixes: commit aa4d86163e4e ("block: loop: switch to VFS ITER_BVEC") Cc: Christoph Hellwig Cc: Al Viro Cc: stable@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: Ming Lei --- drivers/block/loop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index d5fe720cf149..89d2ee00cced 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -266,7 +266,7 @@ static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos) struct iov_iter i; ssize_t bw; - iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len); + iov_iter_bvec(&i, ITER_BVEC | WRITE, bvec, 1, bvec->bv_len); file_start_write(file); bw = vfs_iter_write(file, &i, ppos, 0);