From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757457AbcG1MP2 (ORCPT ); Thu, 28 Jul 2016 08:15:28 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:48253 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757122AbcG1MPU (ORCPT ); Thu, 28 Jul 2016 08:15:20 -0400 From: Vegard Nossum To: linux-mm@kvack.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, Vegard Nossum , "Kirill A. Shutemov" Subject: [PATCH] mm: fail prefaulting if page table allocation fails Date: Thu, 28 Jul 2016 14:15:07 +0200 Message-Id: <1469708107-11868-1-git-send-email-vegard.nossum@oracle.com> X-Mailer: git-send-email 1.9.1 X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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