From dffc6e059e624e32b2cd103726307ad63824c77b Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Thu, 25 Feb 2016 13:00:28 +1100 Subject: [PATCH] thp: do not hold anon_vma lock during swap in khugepaged does swap in during collapse under anon_vma lock. It causes complain from lockdep. The trace below shows following scenario: - khugepaged tries to swap in a page under mmap_sem and anon_vma lock; - do_swap_page() calls swapin_readahead() with GFP_HIGHUSER_MOVABLE; - __read_swap_cache_async() tries to allocate the page for swap in; - lockdep_trace_alloc() in __alloc_pages_nodemask() notices that with given gfp_mask we could end up in direct relaim. - Lockdep already knows that reclaim sometimes (e.g. in case of split_huge_page()) wants to take anon_vma lock on its own. Therefore deadlock is possible. The fix is to take anon_vma lock after swap in. [18344.236625] ================================= [18344.236628] [ INFO: inconsistent lock state ] [18344.236633] 4.3.0-rc1-next-20150918-dbg-00014-ge5128d0-dirty #361 Not tainted [18344.236636] --------------------------------- [18344.236640] inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage. [18344.236645] khugepaged/32 [HC0[0]:SC0[0]:HE1:SE1] takes: [18344.236648] (&anon_vma->rwsem){++++?.}, at: [] khugepaged+0x8b0/0x1987 [18344.236662] {IN-RECLAIM_FS-W} state was registered at: [18344.236666] [] __lock_acquire+0x8e2/0x1183 [18344.236673] [] lock_acquire+0x10b/0x1a6 [18344.236678] [] down_write+0x3b/0x6a [18344.236686] [] split_huge_page_to_list+0x5b/0x61f [18344.236689] [] add_to_swap+0x37/0x78 [18344.236691] [] shrink_page_list+0x4c2/0xb9a [18344.236694] [] shrink_inactive_list+0x371/0x5d9 [18344.236696] [] shrink_lruvec+0x410/0x5ae [18344.236698] [] shrink_zone+0x57/0x140 [18344.236700] [] kswapd+0x6a5/0x91b [18344.236702] [] kthread+0x107/0x10f [18344.236706] [] ret_from_fork+0x3f/0x70 [18344.236708] irq event stamp: 6517947 [18344.236709] hardirqs last enabled at (6517947): [] get_page_from_freelist+0x362/0x59e [18344.236713] hardirqs last disabled at (6517946): [] _raw_spin_lock_irqsave+0x18/0x51 [18344.236715] softirqs last enabled at (6507072): [] __do_softirq+0x2df/0x3f5 [18344.236719] softirqs last disabled at (6507055): [] irq_exit+0x40/0x94 [18344.236722] other info that might help us debug this: [18344.236723] Possible unsafe locking scenario: [18344.236724] CPU0 [18344.236725] ---- [18344.236726] lock(&anon_vma->rwsem); [18344.236728] [18344.236729] lock(&anon_vma->rwsem); [18344.236731] *** DEADLOCK *** [18344.236733] 2 locks held by khugepaged/32: [18344.236733] #0: (&mm->mmap_sem){++++++}, at: [] khugepaged+0x5cf/0x1987 [18344.236738] #1: (&anon_vma->rwsem){++++?.}, at: [] khugepaged+0x8b0/0x1987 [18344.236741] stack backtrace: [18344.236744] CPU: 3 PID: 32 Comm: khugepaged Not tainted 4.3.0-rc1-next-20150918-dbg-00014-ge5128d0-dirty #361 [18344.236747] 0000000000000000 ffff880132827a00 ffffffff81230867 ffffffff8237ba90 [18344.236750] ffff880132827a38 ffffffff810ea9b9 000000000000000a ffff8801333b52e0 [18344.236753] ffff8801333b4c00 ffffffff8107b3ce 000000000000000a ffff880132827a78 [18344.236755] Call Trace: [18344.236758] [] dump_stack+0x4e/0x79 [18344.236761] [] print_usage_bug.part.24+0x259/0x268 [18344.236763] [] ? print_shortest_lock_dependencies+0x180/0x180 [18344.236765] [] mark_lock+0x381/0x567 [18344.236766] [] mark_held_locks+0x5e/0x74 [18344.236768] [] lockdep_trace_alloc+0xb0/0xb3 [18344.236771] [] __alloc_pages_nodemask+0x99/0x856 [18344.236772] [] ? find_get_entry+0x14b/0x17a [18344.236774] [] ? find_get_entry+0x168/0x17a [18344.236777] [] __read_swap_cache_async+0x7b/0x1aa [18344.236778] [] read_swap_cache_async+0x15/0x2d [18344.236780] [] swapin_readahead+0x11a/0x16a [18344.236783] [] do_swap_page+0xa7/0x36b [18344.236784] [] ? do_swap_page+0xa7/0x36b [18344.236787] [] khugepaged+0x8f9/0x1987 [18344.236790] [] ? wait_woken+0x88/0x88 [18344.236792] [] ? maybe_pmd_mkwrite+0x1a/0x1a [18344.236794] [] kthread+0x107/0x10f [18344.236797] [] ? kthread_create_on_node+0x1ea/0x1ea [18344.236799] [] ret_from_fork+0x3f/0x70 [18344.236801] [] ? kthread_create_on_node+0x1ea/0x1ea Signed-off-by: Kirill A. Shutemov Reported-by: Sergey Senozhatsky Tested-by: Sergey Senozhatsky Cc: Ebru Akagunduz Cc: Rik van Riel Cc: Andrea Arcangeli Signed-off-by: Andrew Morton --- mm/huge_memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 794057aa7ee73c..5b38aa24566f19 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2451,10 +2451,10 @@ static void collapse_huge_page(struct mm_struct *mm, goto out; } - anon_vma_lock_write(vma->anon_vma); - __collapse_huge_page_swapin(mm, vma, address, pmd); + anon_vma_lock_write(vma->anon_vma); + pte = pte_offset_map(pmd, address); pte_ptl = pte_lockptr(mm, pmd);