Hugh Dickins wrote: > On Mon, 3 Feb 2014, Sasha Levin wrote: > > On 04/25/2013 10:01 PM, Dave Jones wrote: > > > On Thu, Apr 25, 2013 at 08:51:27PM -0400, Sasha Levin wrote: > > > > On 04/24/2013 06:46 PM, Andrew Morton wrote: > > > > > Guys, did this get fixed? > > > > > > > > I've stopped seeing that during fuzzing, so I guess that it got fixed > > > somehow... > > > > > > We've had reports of users hitting this in 3.8 > > > > > > eg: > > > https://bugzilla.redhat.com/show_bug.cgi?id=947985 > > > https://bugzilla.redhat.com/show_bug.cgi?id=956730 > > > > > > I'm sure there are other reports of it too. > > > > > > Would be good if we can figure out what fixed it (if it is actually fixed) > > > for backporting to stable > > > > It's been a while (7 months?), but this one is back... > > > > Just hit it again with today's -next: > > > > [ 762.701278] BUG: unable to handle kernel paging request at > > ffff88009eae6000 > > [ 762.702462] IP: [<ffffffff81ae8455>] copy_page_rep+0x5/0x10 > > [ 762.703369] PGD 84bb067 PUD 22fa81067 PMD 22f98b067 PTE 800000009eae6060 > > [ 762.704411] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > > [ 762.705873] Dumping ftrace buffer: > > [ 762.707606] (ftrace buffer empty) > > [ 762.708311] Modules linked in: > > [ 762.708762] CPU: 16 PID: 17920 Comm: trinity-c16 Tainted: G W > > 3.13.0-next-2 > > 0140203-sasha-00007-gf4985e2 #23 > > [ 762.710135] task: ffff8801ac358000 ti: ffff880199234000 task.ti: > > ffff880199234000 > > [ 762.710135] RIP: 0010:[<ffffffff81ae8455>] [<ffffffff81ae8455>] > > copy_page_rep+0x5/0x > > 10 > > [ 762.710135] RSP: 0018:ffff880199235c90 EFLAGS: 00010286 > > [ 762.710135] RAX: 0000000080000002 RBX: 00000000056db980 RCX: > > 0000000000000200 > > [ 762.710135] RDX: ffff8801ac358000 RSI: ffff88009eae6000 RDI: > > ffff88015b6e6000 > > [ 762.710135] RBP: ffff880199235cd8 R08: 0000000000000000 R09: > > 0000000000000000 > > [ 762.710135] R10: 0000000000000001 R11: 0000000000000000 R12: > > 00000000027ab980 > > [ 762.710135] R13: 0000000000000200 R14: 00000000000000e6 R15: > > ffff880000000000 > > [ 762.710135] FS: 00007fb0804e1700(0000) GS:ffff88003da00000(0000) > > knlGS:0000000000000 > > 000 > > [ 762.710135] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > [ 762.710135] CR2: ffff88009eae6000 CR3: 0000000199225000 CR4: > > 00000000000006e0 > > [ 762.710135] Stack: > > [ 762.710135] ffffffff81298995 ffff8801a841ae00 ffff88003d084520 > > ffff880199227090 > > [ 762.710135] 800000009ea008e5 ffff8801a841ae00 ffffea00027a8000 > > ffff880199227090 > > [ 762.710135] ffffea00056d8000 ffff880199235d58 ffffffff812d7260 > > ffff880199235cf8 > > [ 762.710135] Call Trace: > > [ 762.710135] [<ffffffff81298995>] ? copy_user_huge_page+0x1a5/0x210 > > [ 762.710135] [<ffffffff812d7260>] do_huge_pmd_wp_page+0x3d0/0x650 > > [ 762.710135] [<ffffffff811a308e>] ? put_lock_stats+0xe/0x30 > > [ 762.710135] [<ffffffff8129b511>] __handle_mm_fault+0x2b1/0x3d0 > > [ 762.710135] [<ffffffff8129b763>] handle_mm_fault+0x133/0x1c0 > > [ 762.710135] [<ffffffff8129bcf8>] __get_user_pages+0x438/0x630 > > [ 762.710135] [<ffffffff811a308e>] ? put_lock_stats+0xe/0x30 > > [ 762.710135] [<ffffffff8129cfc4>] __mlock_vma_pages_range+0xd4/0xe0 > > [ 762.710135] [<ffffffff8129d0e0>] __mm_populate+0x110/0x190 > > [ 762.710135] [<ffffffff8129dcd0>] SyS_mlockall+0x160/0x1b0 > > [ 762.710135] [<ffffffff84450650>] tracesys+0xdd/0xe2 > > [ 762.710135] Code: 90 90 90 90 90 90 9c fa 65 48 3b 06 75 14 65 48 3b 56 08 > > 75 0d 65 48 89 1e 65 48 89 4e 08 9d b0 01 c3 9d 30 c0 c3 b9 00 02 00 00 <f3> > > 48 a5 c3 0f 1f 80 00 > > 00 00 00 eb ee 66 66 66 90 66 66 66 90 > > [ 762.710135] RIP [<ffffffff81ae8455>] copy_page_rep+0x5/0x10 > > [ 762.710135] RSP <ffff880199235c90> > > [ 762.710135] CR2: ffff88009eae6000 > > Here's what I suggested about that one in eecc1e426d68 > "thp: fix copy_page_rep GPF by testing is_huge_zero_pmd once only": > Note: this is not the same issue as trinity's DEBUG_PAGEALLOC BUG > in copy_page_rep with RSI: ffff88009c422000, reported by Sasha Levin > in https://lkml.org/lkml/2013/3/29/103. I believe that one is due > to the source page being split, and a tail page freed, while copy > is in progress; and not a problem without DEBUG_PAGEALLOC, since > the pmd_same check will prevent a miscopy from being made visible. > > It could be fixed by additional locking, or by taking an additional > reference on every tail page, in the DEBUG_PAGEALLOC case (we wouldn't > want to add to the overhead in the normal case). One more nasty idea: invent "safe" variant of copy_user_huge_page(), like safe_copy_page() in kernel/power/snapshot.c. Although, I'm not sure if safe_copy_page() itself safe for races.. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>