From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: [RFC][PATCH] vfs: check inode size on no_cached_page Date: Sun, 12 Apr 2009 15:16:05 +0800 Message-ID: <20090412071605.GA14058@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: LKML , linux-fsdevel@vger.kernel.org, Chenfeng Xu To: Andrew Morton Return-path: Received: from mga14.intel.com ([143.182.124.37]:31531 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756621AbZDLHWh (ORCPT ); Sun, 12 Apr 2009 03:22:37 -0400 Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: [This patch may not necessarily be merged, but at least we should be aware of the problem.] When user space requests past-EOF data, do_generic_file_read() will issue a bonus readpage call, which may be unfavorable. do_generic_file_read: -> find_page: -> find_get_page() = NULL -> page_cache_sync_readahead() -> find_get_page() = NULL -> no_cached_page: -> readpage: -> nfs_readpage() = error -> readpage_error: Reported-by: Xu Chenfeng Signed-off-by: Wu Fengguang --- mm/filemap.c | 5 +++++ 1 file changed, 5 insertions(+) --- mm.orig/mm/filemap.c +++ mm/mm/filemap.c @@ -1269,6 +1269,11 @@ readpage_error: goto out; no_cached_page: + isize = i_size_read(inode); + end_index = (isize - 1) >> PAGE_CACHE_SHIFT; + if (unlikely(!isize || index > end_index)) + goto out; + /* * Ok, it wasn't cached, so we need to create a new * page..