Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753195Ab1E2MQz (ORCPT ); Sun, 29 May 2011 08:16:55 -0400 Received: from mail-pw0-f46.google.com ([209.85.160.46]:47918 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750831Ab1E2MQy (ORCPT ); Sun, 29 May 2011 08:16:54 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:reply-to:organization:to:subject:date:user-agent:cc:references :in-reply-to:mime-version:message-id:content-type :content-transfer-encoding; b=nAQ8tHWjk7MAgvAB2HkQB4YSxCvmiZf8YIMe65EwMzeo8635fa9Nt9MpuXfcov7P7Q lmQFvfy6b0L53qip0YRycm+4psHoSiszRHDJut5n0xKnOxXpOIhb5Jtg0mWmiN4HdTYd znDS3B+ZDPIQ2YM+NtmCbulCJXy1d2TVk3nOo= From: Nai Xia Reply-To: nai.xia@gmail.com Organization: Nanjing University To: Hugh Dickins Subject: Re: [PATCH] mm: fix kernel BUG at mm/rmap.c:1017! Date: Sun, 29 May 2011 20:16:30 +0800 User-Agent: KMail/1.13.5 (Linux/2.6.38.1; KDE/4.5.5; i686; ; ) Cc: Linus Torvalds , Andrew Morton , Shaohua Li , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <201105291823.47082.nai.xia@gmail.com> In-Reply-To: <201105291823.47082.nai.xia@gmail.com> MIME-Version: 1.0 Message-Id: <201105292016.30748.nai.xia@gmail.com> Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2585 Lines: 65 On Sunday 29 May 2011 18:23:46 Nai Xia wrote: > On Sunday 29 May 2011 04:17:04 Hugh Dickins wrote: > > I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap() > > just once. The stack showed khugepaged allocation trying to compact > > pages: the call to page_add_anon_rmap() coming from remove_migration_pte(). > > > > That path holds anon_vma lock, but does not hold mmap_sem: it can > > therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap: > > avoid unnecessary anon_vma lock" we just took away the anon_vma lock > > protection when adjusting vma->vm_end. > > > > I don't think that particular BUG_ON ever caught anything interesting, > > so better replace it by a comment, than reinstate the anon_vma locking. > > Is there another racing between "vma->vm_pgoff = pgoff;" in > vma_adjust() and linear_page_index() in __page_set_anon_rmap() ? Oh, sorry, please ignore this, this _is_ protected by anon_vma lock. Nai Xia > > > Nai Xia > > > > > Signed-off-by: Hugh Dickins > > --- > > mm/rmap.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- linux.orig/mm/rmap.c 2011-05-27 19:05:27.000000000 -0700 > > +++ linux/mm/rmap.c 2011-05-27 20:07:44.601361236 -0700 > > @@ -1014,7 +1014,7 @@ void do_page_add_anon_rmap(struct page * > > return; > > > > VM_BUG_ON(!PageLocked(page)); > > - VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); > > + /* address might be in next vma when migration races vma_adjust */ > > if (first) > > __page_set_anon_rmap(page, vma, address, exclusive); > > else > > @@ -1709,7 +1709,7 @@ void hugepage_add_anon_rmap(struct page > > > > BUG_ON(!PageLocked(page)); > > BUG_ON(!anon_vma); > > - BUG_ON(address < vma->vm_start || address >= vma->vm_end); > > + /* address might be in next vma when migration races vma_adjust */ > > first = atomic_inc_and_test(&page->_mapcount); > > if (first) > > __hugepage_set_anon_rmap(page, vma, address, 0); > > > > -- > > To unsubscribe, send a message with 'unsubscribe linux-mm' in > > the body to majordomo@kvack.org. For more info on Linux MM, > > see: http://www.linux-mm.org/ . > > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > > Don't email: email@kvack.org > > > -- 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/