Messages in this thread | | | Date | Fri, 14 Mar 2014 19:55:19 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH 1/3] mm: munlock: fix a bug where THP tail page is encountered |
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On 12/17/2013 08:00 AM, Vlastimil Babka wrote: > From: Vlastimil Babka<vbabka@suse.cz> > 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 <ffff8805a44c3e08> [ 539.236666] ---[ end trace 4e90dc9141579181 ]---
Thanks, Sasha
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