On 02/06/2013 09:50 PM, Li Zhong wrote: > On Wed, 2013-02-06 at 18:44 -0500, Sasha Levin wrote: >> On 02/04/2013 02:17 AM, Michel Lespinasse wrote: >>> munlock_vma_pages_range() was always incrementing addresses by PAGE_SIZE >>> at a time. When munlocking THP pages (or the huge zero page), this resulted >>> in taking the mm->page_table_lock 512 times in a row. >>> >>> We can do better by making use of the page_mask returned by follow_page_mask >>> (for the huge zero page case), or the size of the page munlock_vma_page() >>> operated on (for the true THP page case). >>> >>> Note - I am sending this as RFC only for now as I can't currently put >>> my finger on what if anything prevents split_huge_page() from operating >>> concurrently on the same page as munlock_vma_page(), which would mess >>> up our NR_MLOCK statistics. Is this a latent bug or is there a subtle >>> point I missed here ? >>> >>> Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> >> >> Hi Michel, >> >> Fuzzing with trinity inside a KVM tools guest produces a steady stream of: >> >> >> [ 51.823275] ------------[ cut here ]------------ >> [ 51.823302] kernel BUG at include/linux/page-flags.h:421! >> [ 51.823307] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >> [ 51.823307] Dumping ftrace buffer: >> [ 51.823314] (ftrace buffer empty) >> [ 51.823314] Modules linked in: >> [ 51.823314] CPU 2 >> [ 51.823314] Pid: 7116, comm: trinity Tainted: G W 3.8.0-rc6-next-20130206-sasha-00027-g3b5963c-dirty #273 >> [ 51.823316] RIP: 0010:[<ffffffff81242792>] [<ffffffff81242792>] munlock_vma_page+0x12/0xf0 >> [ 51.823317] RSP: 0018:ffff880009641bb8 EFLAGS: 00010282 >> [ 51.823319] RAX: 011ffc0000008001 RBX: ffffea0000410040 RCX: 0000000000000000 >> [ 51.823320] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0000410040 >> [ 51.823321] RBP: ffff880009641bc8 R08: 0000000000000000 R09: 0000000000000000 >> [ 51.823322] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880009633958 >> [ 51.823324] R13: 0000000001252000 R14: ffffea0000410040 R15: 00000000000000ff >> [ 51.823326] FS: 00007fe7a9046700(0000) GS:ffff88000ba00000(0000) knlGS:0000000000000000 >> [ 51.823327] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 51.823328] CR2: 00007fc583b90fcb CR3: 0000000009bc8000 CR4: 00000000000406e0 >> [ 51.823334] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> [ 51.823338] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 >> [ 51.823340] Process trinity (pid: 7116, threadinfo ffff880009640000, task ffff880009638000) >> [ 51.823341] Stack: >> [ 51.823344] 0000000000a01000 ffff880009633958 ffff880009641c08 ffffffff812429bd >> [ 51.823373] ffff880009638000 000001ff09638000 ffff880009ade000 ffff880009633958 >> [ 51.823373] ffff880009638810 ffff880009ade098 ffff880009641cb8 ffffffff81246d81 >> [ 51.823373] Call Trace: >> [ 51.823373] [<ffffffff812429bd>] munlock_vma_pages_range+0x8d/0xf0 >> [ 51.823373] [<ffffffff81246d81>] exit_mmap+0x51/0x170 >> [ 51.823373] [<ffffffff81278b4a>] ? __khugepaged_exit+0x8a/0xf0 >> [ 51.823373] [<ffffffff8126a09f>] ? kmem_cache_free+0x22f/0x3b0 >> [ 51.823373] [<ffffffff81278b4a>] ? __khugepaged_exit+0x8a/0xf0 >> [ 51.823373] [<ffffffff8110af97>] mmput+0x77/0xe0 >> [ 51.823377] [<ffffffff81114403>] exit_mm+0x113/0x120 >> [ 51.823381] [<ffffffff83d727f1>] ? _raw_spin_unlock_irq+0x51/0x80 >> [ 51.823384] [<ffffffff8111465a>] do_exit+0x24a/0x590 >> [ 51.823387] [<ffffffff81114a6a>] do_group_exit+0x8a/0xc0 >> [ 51.823390] [<ffffffff81128591>] get_signal_to_deliver+0x501/0x5b0 >> [ 51.823394] [<ffffffff8106dd42>] do_signal+0x42/0x110 >> [ 51.823399] [<ffffffff811d8ea4>] ? rcu_eqs_exit_common+0x64/0x340 >> [ 51.823404] [<ffffffff81184a0d>] ? trace_hardirqs_on+0xd/0x10 >> [ 51.823407] [<ffffffff811849c8>] ? trace_hardirqs_on_caller+0x128/0x160 >> [ 51.823409] [<ffffffff81184a0d>] ? trace_hardirqs_on+0xd/0x10 >> [ 51.823412] [<ffffffff8106de58>] do_notify_resume+0x48/0xa0 >> [ 51.823415] [<ffffffff83d732fb>] retint_signal+0x4d/0x92 >> [ 51.823449] Code: 85 c0 75 0d 48 89 df e8 0d 30 fe ff 0f 1f 44 00 00 48 83 c4 08 5b 5d c3 90 55 48 89 e5 41 54 53 48 89 fb 48 >> 8b 07 f6 c4 80 74 06 <0f> 0b 0f 1f 40 00 48 8b 07 48 c1 e8 0e 83 e0 01 83 f8 01 48 8b >> [ 51.823449] RIP [<ffffffff81242792>] munlock_vma_page+0x12/0xf0 >> [ 51.823450] RSP <ffff880009641bb8> >> [ 51.826846] ---[ end trace a7919e7f17c0a72a ]--- >> > > The similar warning prevents my system from booting. And it seems to me > that in munlock_vma_pages_range(), the page_mask needs be the page > number returned from munlock_vma_page() minus 1. And the following fix > solved my problem. Would you please have a try? Solved it here as well, awesome! Thanks, Sasha -- 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>