Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754623AbdDJPsP (ORCPT ); Mon, 10 Apr 2017 11:48:15 -0400 Received: from mx2.suse.de ([195.135.220.15]:38043 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754538AbdDJPej (ORCPT ); Mon, 10 Apr 2017 11:34:39 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Darrick J. Wong" , Ivan Kozik , Jiri Slaby Subject: [PATCH 3.12 096/142] xfs: clear _XBF_PAGES from buffers when readahead page Date: Mon, 10 Apr 2017 17:32:57 +0200 Message-Id: <6cf4695d5dd09fc8edcb7f6a7c0408a697794fb4.1491838390.git.jslaby@suse.cz> X-Mailer: git-send-email 2.12.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1720 Lines: 48 From: "Darrick J. Wong" 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 2aa6ba7b5ad3189cc27f14540aa2f57f0ed8df4b upstream. If we try to allocate memory pages to back an xfs_buf that we're trying to read, it's possible that we'll be so short on memory that the page allocation fails. For a blocking read we'll just wait, but for readahead we simply dump all the pages we've collected so far. Unfortunately, after dumping the pages we neglect to clear the _XBF_PAGES state, which means that the subsequent call to xfs_buf_free thinks that b_pages still points to pages we own. It then double-frees the b_pages pages. This results in screaming about negative page refcounts from the memory manager, which xfs oughtn't be triggering. To reproduce this case, mount a filesystem where the size of the inodes far outweighs the availalble memory (a ~500M inode filesystem on a VM with 300MB memory did the trick here) and run bulkstat in parallel with other memory eating processes to put a huge load on the system. The "check summary" phase of xfs_scrub also works for this purpose. Signed-off-by: Darrick J. Wong Reviewed-by: Eric Sandeen Cc: Ivan Kozik Signed-off-by: Jiri Slaby --- fs/xfs/xfs_buf.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index c4a4ad0cd33e..e99655a1b372 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -376,6 +376,7 @@ retry: out_free_pages: for (i = 0; i < bp->b_page_count; i++) __free_page(bp->b_pages[i]); + bp->b_flags &= ~_XBF_PAGES; return error; } -- 2.12.2