From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751437AbaCQVIz (ORCPT ); Mon, 17 Mar 2014 17:08:55 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:40454 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750706AbaCQVIy (ORCPT ); Mon, 17 Mar 2014 17:08:54 -0400 Message-ID: <53276452.7040906@oracle.com> Date: Mon, 17 Mar 2014 17:08:34 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Vlastimil Babka , Bob Liu CC: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Rik van Riel , joern@logfs.org, Michel Lespinasse Subject: Re: [PATCH 1/3] mm: munlock: fix a bug where THP tail page is encountered References: <52AE07B4.4020203@oracle.com> <1387188856-21027-1-git-send-email-vbabka@suse.cz> <1387188856-21027-2-git-send-email-vbabka@suse.cz> <52AFA845.3060109@oracle.com> <52B04AD2.2070406@suse.cz> <532396E7.6000400@oracle.com> <5323C3B5.4060602@oracle.com> <5326ECD8.20107@suse.cz> In-Reply-To: <5326ECD8.20107@suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/17/2014 08:38 AM, Vlastimil Babka wrote: > On 03/15/2014 04:06 AM, Sasha Levin wrote: >> On 03/14/2014 07:55 PM, Sasha Levin wrote: >>> On 12/17/2013 08:00 AM, Vlastimil Babka wrote: >>>> From: Vlastimil Babka >>>> Date: Fri, 13 Dec 2013 14:25:21 +0100 >>>> Subject: [PATCH 1/3] mm: munlock: fix a bug where THP tail page is encountered >>>> >>>> Since commit ff6a6da60 ("mm: accelerate munlock() treatment of THP pages") >>>> munlock skips tail pages of a munlocked THP page. However, when the head page >>>> already has PageMlocked unset, it will not skip the tail pages. >>>> >>>> Commit 7225522bb ("mm: munlock: batch non-THP page isolation and >>>> munlock+putback using pagevec") has added a PageTransHuge() check which >>>> contains VM_BUG_ON(PageTail(page)). Sasha Levin found this triggered using >>>> trinity, on the first tail page of a THP page without PageMlocked flag. >>>> >>>> This patch fixes the issue by skipping tail pages also in the case when >>>> PageMlocked flag is unset. There is still a possibility of race with THP page >>>> split between clearing PageMlocked and determining how many pages to skip. >>>> The race might result in former tail pages not being skipped, which is however >>>> no longer a bug, as during the skip the PageTail flags are cleared. >>>> >>>> However this race also affects correctness of NR_MLOCK accounting, which is to >>>> be fixed in a separate patch. >>> >>> I've hit the same thing again, on the latest -next, this time with a different trace: >>> >>> [ 539.199120] page:ffffea0013249a80 count:0 mapcount:1 mapping: (null) index:0x0 >>> [ 539.200429] page flags: 0x12fffff80008000(tail) >>> [ 539.201167] ------------[ cut here ]------------ >>> [ 539.201889] kernel BUG at include/linux/page-flags.h:415! >>> [ 539.202859] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >>> [ 539.204588] Dumping ftrace buffer: >>> [ 539.206415] (ftrace buffer empty) >>> [ 539.207022] Modules linked in: >>> [ 539.207503] CPU: 3 PID: 18262 Comm: trinity-c228 Tainted: G W 3.14.0-rc6-next-20140313-sasha-00010-gb8c1db1-dirty #217 >>> [ 539.209012] task: ffff880627b10000 ti: ffff8805a44c2000 task.ti: ffff8805a44c2000 >>> [ 539.209989] RIP: munlock_vma_pages_range+0x93/0x1d0 (include/linux/page-flags.h:415 mm/mlock.c:494) >>> [ 539.210263] RSP: 0000:ffff8805a44c3e08 EFLAGS: 00010246 >>> [ 539.210263] RAX: ffff88052ae126a0 RBX: 000000000006a000 RCX: 0000000000000099 >>> [ 539.210263] RDX: 0000000000000000 RSI: ffff880627b10cf0 RDI: 0000000004c926a0 >>> [ 539.210263] RBP: ffff8805a44c3ec8 R08: 0000000000000001 R09: 0000000000000001 >>> [ 539.210263] R10: 0000000000000001 R11: 0000000000000001 R12: ffffea0013249a80 >>> [ 539.210263] R13: ffff88039dc95a00 R14: 000000000006b000 R15: ffff8805a44c3e94 >>> [ 539.210263] FS: 00007fd6ce14a700(0000) GS:ffff88042b800000(0000) knlGS:0000000000000000 >>> [ 539.210263] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >>> [ 539.210263] CR2: 00007fd6ce0ef6ac CR3: 00000006025cd000 CR4: 00000000000006a0 >>> [ 539.210263] DR0: 0000000000698000 DR1: 0000000000000000 DR2: 0000000000000000 >>> [ 539.210263] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 >>> [ 539.210263] Stack: >>> [ 539.210263] 0000000000000000 0000000000000000 00018805a44c3e38 0000000000000000 >>> [ 539.210263] 0000000000000000 ffff88039dc95a00 00000000a44c3e88 0000000000000000 >>> [ 539.210263] 00ff8805a44c3e58 ffff880528f0a0f0 ffff8805a44c3eb8 ffff88039dc95a00 >>> [ 539.210263] Call Trace: >>> [ 539.210263] do_munmap+0x1d2/0x360 (mm/internal.h:168 mm/mmap.c:2547) >>> [ 539.210263] ? down_write+0xa6/0xc0 (kernel/locking/rwsem.c:51) >>> [ 539.210263] ? vm_munmap+0x46/0x80 (mm/mmap.c:2571) >>> [ 539.210263] vm_munmap+0x54/0x80 (mm/mmap.c:2572) >>> [ 539.210263] SyS_munmap+0x2c/0x40 (mm/mmap.c:2577) >>> [ 539.210263] tracesys+0xdd/0xe2 (arch/x86/kernel/entry_64.S:749) >>> [ 539.210263] Code: ff 49 89 c4 48 85 c0 0f 84 f3 00 00 00 48 3d 00 f0 ff ff 0f 87 e7 00 00 00 48 8b 00 66 85 c0 79 17 31 f6 4c 89 e7 e8 4d d2 fc ff <0f> 0b 0f 1f 00 eb fe 66 0f 1f 44 00 00 49 8b 04 24 f6 c4 40 74 >>> [ 539.210263] RIP munlock_vma_pages_range+0x93/0x1d0 (include/linux/page-flags.h:415 mm/mlock.c:494) >>> [ 539.210263] RSP >>> [ 539.236666] ---[ end trace 4e90dc9141579181 ]--- >>> >>> >>> Thanks, >>> Sasha >> >> And another related trace: >> >> [ 741.192502] kernel BUG at mm/mlock.c:528! >> [ 741.193088] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >> [ 741.194177] Dumping ftrace buffer: >> [ 741.194645] (ftrace buffer empty) >> [ 741.195109] Modules linked in: >> [ 741.195728] CPU: 23 PID: 19908 Comm: trinity-c264 Tainted: G W 3.14.0-rc6-next-20140314-sasha-00012-g5590866 #219 >> [ 741.197549] task: ffff88061fc2b000 ti: ffff8805decb8000 task.ti: ffff8805decb8000 >> [ 741.198548] RIP: munlock_vma_pages_range+0x176/0x1d0 (mm/mlock.c:528) >> [ 741.199754] RSP: 0018:ffff8805decb9e08 EFLAGS: 00010206 >> [ 741.200085] RAX: 00000000000001ff RBX: 0000000000111000 RCX: 0000000000000000 >> [ 741.200085] RDX: 0000000000000111 RSI: ffffffff81295fdd RDI: ffffffff84490705 >> [ 741.200085] RBP: ffff8805decb9ec8 R08: 0000000000000000 R09: 0000000000000000 >> [ 741.200085] R10: 0000000000000001 R11: 0000000000000000 R12: fffffffffffffff2 >> [ 741.200085] R13: ffff880221044e00 R14: 0000000000112000 R15: ffff8805decb9e94 >> [ 741.200085] FS: 00007f4bec6bc700(0000) GS:ffff88082ba00000(0000) knlGS:0000000000000000 >> [ 741.200085] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >> [ 741.200085] CR2: 0000000003109a98 CR3: 00000005decaf000 CR4: 00000000000006a0 >> [ 741.200085] Stack: >> [ 741.200085] 0000000000000000 0000000000000000 00018805decb9e38 0000000000000000 >> [ 741.200085] 0000000000000000 ffff880221044e00 00000000decb9e88 0000000000000000 >> [ 741.200085] 00ff8805decb9e58 ffff880ff376f450 ffff8805decb9eb8 ffff880221044e00 >> [ 741.200085] Call Trace: >> [ 741.200085] do_munmap+0x1d2/0x360 (mm/internal.h:168 mm/mmap.c:2547) >> [ 741.200085] ? down_write+0xa6/0xc0 (kernel/locking/rwsem.c:51) >> [ 741.200085] ? vm_munmap+0x46/0x80 (mm/mmap.c:2571) >> [ 741.200085] vm_munmap+0x54/0x80 (mm/mmap.c:2572) >> [ 741.200085] SyS_munmap+0x2c/0x40 (mm/mmap.c:2577) >> [ 741.200085] tracesys+0xdd/0xe2 (arch/x86/kernel/entry_64.S:749) >> [ 741.200085] Code: fd ff ff 4c 89 e6 48 89 c3 48 8d bd 40 ff ff ff e8 80 fa ff ff eb 2f 66 0f 1f 44 00 00 8b 45 cc 48 89 da 48 c1 ea 0c 85 d0 74 12 <0f> 0b 0f 1f 84 00 00 00 00 00 eb fe 66 0f 1f 44 00 00 ff c0 48 >> [ 741.200085] RIP munlock_vma_pages_range+0x176/0x1d0 (mm/mlock.c:528) >> [ 741.200085] RSP > > Sigh, again? I really wonder what is it this time :) > Please try this debug patch, hopefully we learn something: > > diff --git a/mm/mlock.c b/mm/mlock.c > index 4e1a6816..7094bac 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -469,12 +469,14 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, > void munlock_vma_pages_range(struct vm_area_struct *vma, > unsigned long start, unsigned long end) > { > + unsigned long orig_start = start; > + unsigned long page_increm = 0; > + > vma->vm_flags &= ~VM_LOCKED; > > while (start < end) { > struct page *page = NULL; > unsigned int page_mask; > - unsigned long page_increm; > struct pagevec pvec; > struct zone *zone; > int zoneid; > @@ -491,6 +493,24 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, > &page_mask); > > if (page && !IS_ERR(page)) { > + if (PageTail(page)) { > + struct page *first_page; > + dump_page(page, "Unexpected PageTail"); > + printk("start=%lu pfn=%lu orig_start=%lu " > + "page_increm=%lu " > + "vm_start=%lu vm_end=%lu vm_flags=%lu\n", > + start, page_to_pfn(page), orig_start, > + page_increm, > + vma->vm_start, vma->vm_end, > + vma->vm_flags); > + first_page = page->first_page; > + printk("first_page pfn=%lu\n", > + page_to_pfn(first_page)); > + dump_page(first_page, "first_page of unexpected PageTail page"); > + if (PageCompound(first_page)) > + printk("first_page is compound with order=%d\n", compound_order(first_page)); > + VM_BUG_ON(true); > + } > if (PageTransHuge(page)) { > lock_page(page); > /* > @@ -525,7 +545,25 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, > } > } > /* It's a bug to munlock in the middle of a THP page */ > - VM_BUG_ON((start >> PAGE_SHIFT) & page_mask); > + if ((start >> PAGE_SHIFT) & page_mask) { > + dump_page(page, "unexpected middle of THP page"); > + printk("start=%lu pfn=%lu orig_start=%lu " In this scenario page might be error or NULL, no? Thanks, Sasha From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f44.google.com (mail-pb0-f44.google.com [209.85.160.44]) by kanga.kvack.org (Postfix) with ESMTP id 941E06B00D2 for ; Mon, 17 Mar 2014 17:17:55 -0400 (EDT) Received: by mail-pb0-f44.google.com with SMTP id rp16so6277689pbb.3 for ; Mon, 17 Mar 2014 14:17:55 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id yo5si10861252pab.210.2014.03.17.14.17.53 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 17 Mar 2014 14:17:54 -0700 (PDT) Message-ID: <53276452.7040906@oracle.com> Date: Mon, 17 Mar 2014 17:08:34 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: [PATCH 1/3] mm: munlock: fix a bug where THP tail page is encountered References: <52AE07B4.4020203@oracle.com> <1387188856-21027-1-git-send-email-vbabka@suse.cz> <1387188856-21027-2-git-send-email-vbabka@suse.cz> <52AFA845.3060109@oracle.com> <52B04AD2.2070406@suse.cz> <532396E7.6000400@oracle.com> <5323C3B5.4060602@oracle.com> <5326ECD8.20107@suse.cz> In-Reply-To: <5326ECD8.20107@suse.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Bob Liu Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Rik van Riel , joern@logfs.org, Michel Lespinasse On 03/17/2014 08:38 AM, Vlastimil Babka wrote: > On 03/15/2014 04:06 AM, Sasha Levin wrote: >> On 03/14/2014 07:55 PM, Sasha Levin wrote: >>> On 12/17/2013 08:00 AM, Vlastimil Babka wrote: >>>> From: Vlastimil Babka >>>> Date: Fri, 13 Dec 2013 14:25:21 +0100 >>>> Subject: [PATCH 1/3] mm: munlock: fix a bug where THP tail page is encountered >>>> >>>> Since commit ff6a6da60 ("mm: accelerate munlock() treatment of THP pages") >>>> munlock skips tail pages of a munlocked THP page. However, when the head page >>>> already has PageMlocked unset, it will not skip the tail pages. >>>> >>>> Commit 7225522bb ("mm: munlock: batch non-THP page isolation and >>>> munlock+putback using pagevec") has added a PageTransHuge() check which >>>> contains VM_BUG_ON(PageTail(page)). Sasha Levin found this triggered using >>>> trinity, on the first tail page of a THP page without PageMlocked flag. >>>> >>>> This patch fixes the issue by skipping tail pages also in the case when >>>> PageMlocked flag is unset. There is still a possibility of race with THP page >>>> split between clearing PageMlocked and determining how many pages to skip. >>>> The race might result in former tail pages not being skipped, which is however >>>> no longer a bug, as during the skip the PageTail flags are cleared. >>>> >>>> However this race also affects correctness of NR_MLOCK accounting, which is to >>>> be fixed in a separate patch. >>> >>> I've hit the same thing again, on the latest -next, this time with a different trace: >>> >>> [ 539.199120] page:ffffea0013249a80 count:0 mapcount:1 mapping: (null) index:0x0 >>> [ 539.200429] page flags: 0x12fffff80008000(tail) >>> [ 539.201167] ------------[ cut here ]------------ >>> [ 539.201889] kernel BUG at include/linux/page-flags.h:415! >>> [ 539.202859] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >>> [ 539.204588] Dumping ftrace buffer: >>> [ 539.206415] (ftrace buffer empty) >>> [ 539.207022] Modules linked in: >>> [ 539.207503] CPU: 3 PID: 18262 Comm: trinity-c228 Tainted: G W 3.14.0-rc6-next-20140313-sasha-00010-gb8c1db1-dirty #217 >>> [ 539.209012] task: ffff880627b10000 ti: ffff8805a44c2000 task.ti: ffff8805a44c2000 >>> [ 539.209989] RIP: munlock_vma_pages_range+0x93/0x1d0 (include/linux/page-flags.h:415 mm/mlock.c:494) >>> [ 539.210263] RSP: 0000:ffff8805a44c3e08 EFLAGS: 00010246 >>> [ 539.210263] RAX: ffff88052ae126a0 RBX: 000000000006a000 RCX: 0000000000000099 >>> [ 539.210263] RDX: 0000000000000000 RSI: ffff880627b10cf0 RDI: 0000000004c926a0 >>> [ 539.210263] RBP: ffff8805a44c3ec8 R08: 0000000000000001 R09: 0000000000000001 >>> [ 539.210263] R10: 0000000000000001 R11: 0000000000000001 R12: ffffea0013249a80 >>> [ 539.210263] R13: ffff88039dc95a00 R14: 000000000006b000 R15: ffff8805a44c3e94 >>> [ 539.210263] FS: 00007fd6ce14a700(0000) GS:ffff88042b800000(0000) knlGS:0000000000000000 >>> [ 539.210263] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >>> [ 539.210263] CR2: 00007fd6ce0ef6ac CR3: 00000006025cd000 CR4: 00000000000006a0 >>> [ 539.210263] DR0: 0000000000698000 DR1: 0000000000000000 DR2: 0000000000000000 >>> [ 539.210263] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 >>> [ 539.210263] Stack: >>> [ 539.210263] 0000000000000000 0000000000000000 00018805a44c3e38 0000000000000000 >>> [ 539.210263] 0000000000000000 ffff88039dc95a00 00000000a44c3e88 0000000000000000 >>> [ 539.210263] 00ff8805a44c3e58 ffff880528f0a0f0 ffff8805a44c3eb8 ffff88039dc95a00 >>> [ 539.210263] Call Trace: >>> [ 539.210263] do_munmap+0x1d2/0x360 (mm/internal.h:168 mm/mmap.c:2547) >>> [ 539.210263] ? down_write+0xa6/0xc0 (kernel/locking/rwsem.c:51) >>> [ 539.210263] ? vm_munmap+0x46/0x80 (mm/mmap.c:2571) >>> [ 539.210263] vm_munmap+0x54/0x80 (mm/mmap.c:2572) >>> [ 539.210263] SyS_munmap+0x2c/0x40 (mm/mmap.c:2577) >>> [ 539.210263] tracesys+0xdd/0xe2 (arch/x86/kernel/entry_64.S:749) >>> [ 539.210263] Code: ff 49 89 c4 48 85 c0 0f 84 f3 00 00 00 48 3d 00 f0 ff ff 0f 87 e7 00 00 00 48 8b 00 66 85 c0 79 17 31 f6 4c 89 e7 e8 4d d2 fc ff <0f> 0b 0f 1f 00 eb fe 66 0f 1f 44 00 00 49 8b 04 24 f6 c4 40 74 >>> [ 539.210263] RIP munlock_vma_pages_range+0x93/0x1d0 (include/linux/page-flags.h:415 mm/mlock.c:494) >>> [ 539.210263] RSP >>> [ 539.236666] ---[ end trace 4e90dc9141579181 ]--- >>> >>> >>> Thanks, >>> Sasha >> >> And another related trace: >> >> [ 741.192502] kernel BUG at mm/mlock.c:528! >> [ 741.193088] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >> [ 741.194177] Dumping ftrace buffer: >> [ 741.194645] (ftrace buffer empty) >> [ 741.195109] Modules linked in: >> [ 741.195728] CPU: 23 PID: 19908 Comm: trinity-c264 Tainted: G W 3.14.0-rc6-next-20140314-sasha-00012-g5590866 #219 >> [ 741.197549] task: ffff88061fc2b000 ti: ffff8805decb8000 task.ti: ffff8805decb8000 >> [ 741.198548] RIP: munlock_vma_pages_range+0x176/0x1d0 (mm/mlock.c:528) >> [ 741.199754] RSP: 0018:ffff8805decb9e08 EFLAGS: 00010206 >> [ 741.200085] RAX: 00000000000001ff RBX: 0000000000111000 RCX: 0000000000000000 >> [ 741.200085] RDX: 0000000000000111 RSI: ffffffff81295fdd RDI: ffffffff84490705 >> [ 741.200085] RBP: ffff8805decb9ec8 R08: 0000000000000000 R09: 0000000000000000 >> [ 741.200085] R10: 0000000000000001 R11: 0000000000000000 R12: fffffffffffffff2 >> [ 741.200085] R13: ffff880221044e00 R14: 0000000000112000 R15: ffff8805decb9e94 >> [ 741.200085] FS: 00007f4bec6bc700(0000) GS:ffff88082ba00000(0000) knlGS:0000000000000000 >> [ 741.200085] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >> [ 741.200085] CR2: 0000000003109a98 CR3: 00000005decaf000 CR4: 00000000000006a0 >> [ 741.200085] Stack: >> [ 741.200085] 0000000000000000 0000000000000000 00018805decb9e38 0000000000000000 >> [ 741.200085] 0000000000000000 ffff880221044e00 00000000decb9e88 0000000000000000 >> [ 741.200085] 00ff8805decb9e58 ffff880ff376f450 ffff8805decb9eb8 ffff880221044e00 >> [ 741.200085] Call Trace: >> [ 741.200085] do_munmap+0x1d2/0x360 (mm/internal.h:168 mm/mmap.c:2547) >> [ 741.200085] ? down_write+0xa6/0xc0 (kernel/locking/rwsem.c:51) >> [ 741.200085] ? vm_munmap+0x46/0x80 (mm/mmap.c:2571) >> [ 741.200085] vm_munmap+0x54/0x80 (mm/mmap.c:2572) >> [ 741.200085] SyS_munmap+0x2c/0x40 (mm/mmap.c:2577) >> [ 741.200085] tracesys+0xdd/0xe2 (arch/x86/kernel/entry_64.S:749) >> [ 741.200085] Code: fd ff ff 4c 89 e6 48 89 c3 48 8d bd 40 ff ff ff e8 80 fa ff ff eb 2f 66 0f 1f 44 00 00 8b 45 cc 48 89 da 48 c1 ea 0c 85 d0 74 12 <0f> 0b 0f 1f 84 00 00 00 00 00 eb fe 66 0f 1f 44 00 00 ff c0 48 >> [ 741.200085] RIP munlock_vma_pages_range+0x176/0x1d0 (mm/mlock.c:528) >> [ 741.200085] RSP > > Sigh, again? I really wonder what is it this time :) > Please try this debug patch, hopefully we learn something: > > diff --git a/mm/mlock.c b/mm/mlock.c > index 4e1a6816..7094bac 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -469,12 +469,14 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec, > void munlock_vma_pages_range(struct vm_area_struct *vma, > unsigned long start, unsigned long end) > { > + unsigned long orig_start = start; > + unsigned long page_increm = 0; > + > vma->vm_flags &= ~VM_LOCKED; > > while (start < end) { > struct page *page = NULL; > unsigned int page_mask; > - unsigned long page_increm; > struct pagevec pvec; > struct zone *zone; > int zoneid; > @@ -491,6 +493,24 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, > &page_mask); > > if (page && !IS_ERR(page)) { > + if (PageTail(page)) { > + struct page *first_page; > + dump_page(page, "Unexpected PageTail"); > + printk("start=%lu pfn=%lu orig_start=%lu " > + "page_increm=%lu " > + "vm_start=%lu vm_end=%lu vm_flags=%lu\n", > + start, page_to_pfn(page), orig_start, > + page_increm, > + vma->vm_start, vma->vm_end, > + vma->vm_flags); > + first_page = page->first_page; > + printk("first_page pfn=%lu\n", > + page_to_pfn(first_page)); > + dump_page(first_page, "first_page of unexpected PageTail page"); > + if (PageCompound(first_page)) > + printk("first_page is compound with order=%d\n", compound_order(first_page)); > + VM_BUG_ON(true); > + } > if (PageTransHuge(page)) { > lock_page(page); > /* > @@ -525,7 +545,25 @@ void munlock_vma_pages_range(struct vm_area_struct *vma, > } > } > /* It's a bug to munlock in the middle of a THP page */ > - VM_BUG_ON((start >> PAGE_SHIFT) & page_mask); > + if ((start >> PAGE_SHIFT) & page_mask) { > + dump_page(page, "unexpected middle of THP page"); > + printk("start=%lu pfn=%lu orig_start=%lu " In this scenario page might be error or NULL, no? Thanks, Sasha -- 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