From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:57390 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306AbdC1MOY (ORCPT ); Tue, 28 Mar 2017 08:14:24 -0400 Subject: Patch "xfs: clear _XBF_PAGES from buffers when readahead page" has been added to the 4.4-stable tree To: darrick.wong@oracle.com, gregkh@linuxfoundation.org, ivan@ludios.org, sandeen@redhat.com Cc: , From: Date: Tue, 28 Mar 2017 14:13:46 +0200 Message-ID: <1490703226246234@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled xfs: clear _XBF_PAGES from buffers when readahead page to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: xfs-clear-_xbf_pages-from-buffers-when-readahead-page.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 2aa6ba7b5ad3189cc27f14540aa2f57f0ed8df4b Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 25 Jan 2017 20:24:57 -0800 Subject: xfs: clear _XBF_PAGES from buffers when readahead page From: Darrick J. Wong 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: Greg Kroah-Hartman --- fs/xfs/xfs_buf.c | 1 + 1 file changed, 1 insertion(+) --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -375,6 +375,7 @@ 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; } Patches currently in stable-queue which might be from darrick.wong@oracle.com are queue-4.4/xfs-don-t-allow-di_size-with-high-bit-set.patch queue-4.4/xfs-clear-_xbf_pages-from-buffers-when-readahead-page.patch