Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030392AbWJCRv7 (ORCPT ); Tue, 3 Oct 2006 13:51:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030395AbWJCRv6 (ORCPT ); Tue, 3 Oct 2006 13:51:58 -0400 Received: from mx1.redhat.com ([66.187.233.31]:30944 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1030392AbWJCRv5 (ORCPT ); Tue, 3 Oct 2006 13:51:57 -0400 Date: Tue, 3 Oct 2006 13:51:49 -0400 (EDT) From: Chip Coldwell To: linux-kernel@vger.kernel.org cc: akpm@osdl.org Subject: direct IO regression in 2.6.18 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2357 Lines: 75 Hi, The following commit caused a regression in direct IO: commit 016eb4a0ed06a3677d67a584da901f0e9a63c666 Author: Andrew Morton Date: Fri Sep 8 09:48:38 2006 -0700 [PATCH] invalidate_complete_page() race fix If a CPU faults this page into pagetables after invalidate_mapping_pages() checked page_mapped(), invalidate_complete_page() will still proceed to remove the page from pagecache. This leaves the page-faulting process with a detached page. If it was MAP_SHARED then file data loss will ensue. Fix that up by checking the page's refcount after taking tree_lock. Cc: Nick Piggin Cc: Hugh Dickins Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/mm/truncate.c b/mm/truncate.c index cf1b015..c6ab55e 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -68,10 +68,10 @@ invalidate_complete_page(struct address_ return 0; write_lock_irq(&mapping->tree_lock); - if (PageDirty(page)) { - write_unlock_irq(&mapping->tree_lock); - return 0; - } + if (PageDirty(page)) + goto failed; + if (page_count(page) != 2) /* caller's ref + pagecache ref */ + goto failed; BUG_ON(PagePrivate(page)); __remove_from_page_cache(page); @@ -79,6 +79,9 @@ invalidate_complete_page(struct address_ ClearPageUptodate(page); page_cache_release(page); /* pagecache ref */ return 1; +failed: + write_unlock_irq(&mapping->tree_lock); + return 0; } /** The issue is that invalidate_complete_page is in two different code paths, the normal one (prune_icache calls invalidate_inode_pages calls invalidate_mapping_pages calls invalidate_complete_page) and also via direct IO (generic_file_direct_write calls generic_file_direct_IO calls invalidate_inode_pages2_range calls invalidate_complete_page). In the latter case, the page is (usually) not even in the page cache and the refcount can legitimately != 2. Chip -- Charles M. "Chip" Coldwell Senior Software Engineer Red Hat, Inc 978-392-2426 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/