From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f70.google.com (mail-lf0-f70.google.com [209.85.215.70]) by kanga.kvack.org (Postfix) with ESMTP id 944C66B0253 for ; Thu, 28 Jul 2016 08:21:41 -0400 (EDT) Received: by mail-lf0-f70.google.com with SMTP id 33so15403248lfw.1 for ; Thu, 28 Jul 2016 05:21:41 -0700 (PDT) Received: from mail-lf0-x242.google.com (mail-lf0-x242.google.com. [2a00:1450:4010:c07::242]) by mx.google.com with ESMTPS id a140si5931747lfa.176.2016.07.28.05.21.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Jul 2016 05:21:40 -0700 (PDT) Received: by mail-lf0-x242.google.com with SMTP id l89so3581964lfi.2 for ; Thu, 28 Jul 2016 05:21:40 -0700 (PDT) Date: Thu, 28 Jul 2016 15:21:37 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] mm: fail prefaulting if page table allocation fails Message-ID: <20160728122137.GA24367@node.shutemov.name> References: <1469708107-11868-1-git-send-email-vegard.nossum@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1469708107-11868-1-git-send-email-vegard.nossum@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vegard Nossum Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" On Thu, Jul 28, 2016 at 02:15:07PM +0200, Vegard Nossum wrote: > I ran into this: > > BUG: sleeping function called from invalid context at mm/page_alloc.c:3784 > in_atomic(): 0, irqs_disabled(): 0, pid: 1434, name: trinity-c1 > 2 locks held by trinity-c1/1434: > #0: (&mm->mmap_sem){......}, at: [] __do_page_fault+0x1ce/0x8f0 > #1: (rcu_read_lock){......}, at: [] filemap_map_pages+0xd6/0xdd0 > > CPU: 0 PID: 1434 Comm: trinity-c1 Not tainted 4.7.0+ #58 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 > ffff8800b662f698 ffff8800b662f548 ffffffff81d6d001 ffffffff83a61100 > ffff8800b662f620 ffff8800b662f610 ffffffff81373fd1 0000000041b58ab3 > ffffffff8406ca21 ffffffff81373e4c 0000000041b58ab3 ffffffff00000008 > Call Trace: > [] dump_stack+0x65/0x84 > [] panic+0x185/0x2dd > [] ___might_sleep+0x51c/0x600 > [] __might_sleep+0x90/0x1a0 > [] __alloc_pages_nodemask+0x5b1/0x2160 > [] alloc_pages_current+0xcc/0x370 > [] pte_alloc_one+0x12/0x90 > [] __pte_alloc+0x1d/0x200 > [] alloc_set_pte+0xe3e/0x14a0 > [] filemap_map_pages+0x42b/0xdd0 > [] handle_mm_fault+0x17d5/0x28b0 > [] __do_page_fault+0x310/0x8f0 > [] trace_do_page_fault+0x18d/0x310 > [] do_async_page_fault+0x27/0xa0 > [] async_page_fault+0x28/0x30 > > The important bits from the above is that filemap_map_pages() is calling > into the page allocator while holding rcu_read_lock (sleeping is not > allowed inside RCU read-side critical sections). > > According to Kirill Shutemov, the prefaulting code in do_fault_around() > is supposed to take care of this, but missing error handling means that > the allocation failure can go unnoticed. > > We don't need to return VM_FAULT_OOM (or any other error) here, since we > can just let the normal fault path try again. > > Fixes: 7267ec008b5c ("mm: postpone page table allocation until we have page to map") > Cc: Kirill A. Shutemov > Signed-off-by: Vegard Nossum Acked-by: Kirill A. Shutemov Worth noticing that it's failure of order-0 allocation and unlikely to ever happen under normal workloads without fault injection for page allocator. > --- > mm/memory.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 4425b60..0400483 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3133,6 +3133,8 @@ static int do_fault_around(struct fault_env *fe, pgoff_t start_pgoff) > > if (pmd_none(*fe->pmd)) { > fe->prealloc_pte = pte_alloc_one(fe->vma->vm_mm, fe->address); > + if (!fe->prealloc_pte) > + goto out; > smp_wmb(); /* See comment in __pte_alloc() */ > } > > -- > 1.9.1 > > -- > 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/ . > Don't email: email@kvack.org -- Kirill A. Shutemov -- 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/ . Don't email: email@kvack.org