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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 432E9C433DF for ; Thu, 20 Aug 2020 09:58:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C2DD20855 for ; Thu, 20 Aug 2020 09:58:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597917504; bh=B9I86CKSfEkWeYcKIy1EwsYk+OARDO/f2z7E9feAlY0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mGM30rhCmBMYFJFIX1WKydvPr4L5Yj89sqL1idu3JK+v9VHJnIVwGQJ5kQTriXSr7 FHFbeYRPOn1dSw4f3XaX6QNaDblsYNvrq79b80jiKiwP1/5npJoE68GGiY8yarZQUr 3k5lpQHtj9cHX8yhQPvlwxByX7sU7nnds9CympKU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730394AbgHTJ6R (ORCPT ); Thu, 20 Aug 2020 05:58:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:42012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726796AbgHTJ6M (ORCPT ); Thu, 20 Aug 2020 05:58:12 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DBB972067C; Thu, 20 Aug 2020 09:58:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597917491; bh=B9I86CKSfEkWeYcKIy1EwsYk+OARDO/f2z7E9feAlY0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GlIUtJMwzvGRN04NkHsfNsJ1WbeuRyXWum3ATxaG2TtJzhUfKsAQl31Wu1Gwo9818 D582SD722ixq5tWczw9Rp8l4toYWHaC8XsEkE/PEz6lvk40+s7QJC3BQElc/0ym/B9 baWfN2yKa+LuMgLGBp0goFEjTGAyjXoEo1xLWTJI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara , Wang Long , Jiang Ying Subject: [PATCH 4.9 050/212] ext4: fix direct I/O read error Date: Thu, 20 Aug 2020 11:20:23 +0200 Message-Id: <20200820091604.894804916@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200820091602.251285210@linuxfoundation.org> References: <20200820091602.251285210@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiang Ying This patch is used to fix ext4 direct I/O read error when the read size is not aligned with block size. Then, I will use a test to explain the error. (1) Make a file that is not aligned with block size: $dd if=/dev/zero of=./test.jar bs=1000 count=3 (2) I wrote a source file named "direct_io_read_file.c" as following: #include #include #include #include #include #include #include #define BUF_SIZE 1024 int main() { int fd; int ret; unsigned char *buf; ret = posix_memalign((void **)&buf, 512, BUF_SIZE); if (ret) { perror("posix_memalign failed"); exit(1); } fd = open("./test.jar", O_RDONLY | O_DIRECT, 0755); if (fd < 0){ perror("open ./test.jar failed"); exit(1); } do { ret = read(fd, buf, BUF_SIZE); printf("ret=%d\n",ret); if (ret < 0) { perror("write test.jar failed"); } } while (ret > 0); free(buf); close(fd); } (3) Compile the source file: $gcc direct_io_read_file.c -D_GNU_SOURCE (4) Run the test program: $./a.out The result is as following: ret=1024 ret=1024 ret=952 ret=-1 write test.jar failed: Invalid argument. I have tested this program on XFS filesystem, XFS does not have this problem, because XFS use iomap_dio_rw() to do direct I/O read. And the comparing between read offset and file size is done in iomap_dio_rw(), the code is as following: if (pos < size) { retval = filemap_write_and_wait_range(mapping, pos, pos + iov_length(iov, nr_segs) - 1); if (!retval) { retval = mapping->a_ops->direct_IO(READ, iocb, iov, pos, nr_segs); } ... } ...only when "pos < size", direct I/O can be done, or 0 will be return. I have tested the fix patch on Ext4, it is up to the mustard of EINVAL in man2(read) as following: #include ssize_t read(int fd, void *buf, size_t count); EINVAL fd is attached to an object which is unsuitable for reading; or the file was opened with the O_DIRECT flag, and either the address specified in buf, the value specified in count, or the current file offset is not suitably aligned. So I think this patch can be applied to fix ext4 direct I/O error. However Ext4 introduces direct I/O read using iomap infrastructure on kernel 5.5, the patch is commit ("ext4: introduce direct I/O read using iomap infrastructure"), then Ext4 will be the same as XFS, they all use iomap_dio_rw() to do direct I/O read. So this problem does not exist on kernel 5.5 for Ext4. >>From above description, we can see this problem exists on all the kernel versions between kernel 3.14 and kernel 5.4. It will cause the Applications to fail to read. For example, when the search service downloads a new full index file, the search engine is loading the previous index file and is processing the search request, it can not use buffer io that may squeeze the previous index file in use from pagecache, so the serch service must use direct I/O read. Please apply this patch on these kernel versions, or please use the method on kernel 5.5 to fix this problem. Fixes: 9fe55eea7e4b ("Fix race when checking i_size on direct i/o read") Reviewed-by: Jan Kara Reviewed-by: Wang Long Signed-off-by: Jiang Ying Signed-off-by: Greg Kroah-Hartman --- fs/ext4/inode.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3575,6 +3575,11 @@ static ssize_t ext4_direct_IO_read(struc struct address_space *mapping = iocb->ki_filp->f_mapping; struct inode *inode = mapping->host; ssize_t ret; + loff_t offset = iocb->ki_pos; + loff_t size = i_size_read(inode); + + if (offset >= size) + return 0; /* * Shared inode_lock is enough for us - it protects against concurrent