From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: [PATCH] xfs: handle EOF correctly in xfs_vm_writepage Date: Tue, 3 Jul 2012 12:20:00 -0400 Message-ID: <20120703162000.GA13016@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Yongqiang Yang , linux-fsdevel@vger.kernel.org To: xfs@oss.sgi.com Return-path: Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:43770 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754050Ab2GCQUC (ORCPT ); Tue, 3 Jul 2012 12:20:02 -0400 Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: We need to zero out part of a page which beyond EOF before setting uptodate, otherwise, mapread or write will see non-zero data beyond EOF. Based on the code in fs/buffer.c and the following ext4 commit: ext4: handle EOF correctly in ext4_bio_write_page() And yes, I wish we had a good test case for it. Signed-off-by: Christoph Hellwig --- fs/xfs/xfs_aops.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) Index: xfs/fs/xfs/xfs_aops.c =================================================================== --- xfs.orig/fs/xfs/xfs_aops.c 2012-06-26 23:20:22.286407388 +0200 +++ xfs/fs/xfs/xfs_aops.c 2012-06-26 23:21:49.323073534 +0200 @@ -927,11 +927,26 @@ xfs_vm_writepage( end_index = offset >> PAGE_CACHE_SHIFT; last_index = (offset - 1) >> PAGE_CACHE_SHIFT; if (page->index >= end_index) { - if ((page->index >= end_index + 1) || - !(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) { + unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1); + + /* + * Just skip the page if it is fully outside i_size, e.g. due + * to a truncate operation that is in progress. + */ + if (page->index >= end_index + 1 || offset_into_page == 0) { unlock_page(page); return 0; } + + /* + * The page straddles i_size. It must be zeroed out on each + * and every writepage invocation because it may be mmapped. + * "A file is mapped in multiples of the page size. For a file + * that is not a multiple of the page size, the remaining + * memory is zeroed when mapped, and writes to that region are + * not written out to the file." + */ + zero_user_segment(page, offset_into_page, PAGE_CACHE_SIZE); } end_offset = min_t(unsigned long long,