Hi Vlastimil, On Wed, Dec 18, 2013 at 09:54:16AM +0100, Vlastimil Babka wrote: >On 12/17/2013 09:05 AM, Wanpeng Li wrote: >>objrmap doesn't work for nonlinear VMAs because the assumption that offset-into-file >>correlates with offset-into-virtual-addresses does not hold. Hence what >>try_to_unmap_cluster does is a mini "virtual scan" of each nonlinear VMA which maps >>the file to which the target page belongs. If vma locked, mlock the pages in the >>cluster, rather than unmapping them. However, not all pages are guarantee page >>locked instead of the check page. This patch fix the BUG by just confirm check page >>hold page lock instead of all pages in the virtual scan window against nolinear VMAs. > >This may fix the symptom, but I don't understand from the description >why in this case is it ok not to have page locked for >mlock_vma_page(), while in the other cases it's not ok. > Here is a latest version of the bugfix patch. http://marc.info/?l=linux-mm&m=138733994417230&w=2 Regards, Wanpeng Li >>[ 253.869145] kernel BUG at mm/mlock.c:82! >>[ 253.869549] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >>[ 253.870098] Dumping ftrace buffer: >>[ 253.870098] (ftrace buffer empty) >>[ 253.870098] Modules linked in: >>[ 253.870098] CPU: 10 PID: 9162 Comm: trinity-child75 Tainted: G W 3.13.0-rc4-next-20131216-sasha-00011-g5f105ec-dirty #4137 >>[ 253.873310] task: ffff8800c98cb000 ti: ffff8804d34e8000 task.ti: ffff8804d34e8000 >>[ 253.873310] RIP: 0010:[<ffffffff81281f28>] [<ffffffff81281f28>] mlock_vma_page+0x18/0xc0 >>[ 253.873310] RSP: 0000:ffff8804d34e99e8 EFLAGS: 00010246 >>[ 253.873310] RAX: 006fffff8038002c RBX: ffffea00474944c0 RCX: ffff880807636000 >>[ 253.873310] RDX: ffffea0000000000 RSI: 00007f17a9bca000 RDI: ffffea00474944c0 >>[ 253.873310] RBP: ffff8804d34e99f8 R08: ffff880807020000 R09: 0000000000000000 >>[ 253.873310] R10: 0000000000000001 R11: 0000000000002000 R12: 00007f17a9bca000 >>[ 253.873310] R13: ffffea00474944c0 R14: 00007f17a9be0000 R15: ffff880807020000 >>[ 253.873310] FS: 00007f17aa31a700(0000) GS:ffff8801c9c00000(0000) knlGS:0000000000000000 >>[ 253.873310] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >>[ 253.873310] CR2: 00007f17a94fa000 CR3: 00000004d3b02000 CR4: 00000000000006e0 >>[ 253.873310] DR0: 00007f17a74ca000 DR1: 0000000000000000 DR2: 0000000000000000 >>[ 253.873310] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 >>[ 253.873310] Stack: >>[ 253.873310] 0000000b3de28067 ffff880b3de28e50 ffff8804d34e9aa8 ffffffff8128bc31 >>[ 253.873310] 0000000000000301 ffffea0011850220 ffff8809a4039000 ffffea0011850238 >>[ 253.873310] ffff8804d34e9aa8 ffff880807636060 0000000000000001 ffff880807636348 >>[ 253.873310] Call Trace: >>[ 253.873310] [<ffffffff8128bc31>] try_to_unmap_cluster+0x1c1/0x340 >>[ 253.873310] [<ffffffff8128c60a>] try_to_unmap_file+0x20a/0x2e0 >>[ 253.873310] [<ffffffff8128c7b3>] try_to_unmap+0x73/0x90 >>[ 253.873310] [<ffffffff812b526d>] __unmap_and_move+0x18d/0x250 >>[ 253.873310] [<ffffffff812b53e9>] unmap_and_move+0xb9/0x180 >>[ 253.873310] [<ffffffff812b559b>] migrate_pages+0xeb/0x2f0 >>[ 253.873310] [<ffffffff812a0660>] ? queue_pages_pte_range+0x1a0/0x1a0 >>[ 253.873310] [<ffffffff812a193c>] migrate_to_node+0x9c/0xc0 >>[ 253.873310] [<ffffffff812a30b8>] do_migrate_pages+0x1b8/0x240 >>[ 253.873310] [<ffffffff812a3456>] SYSC_migrate_pages+0x316/0x380 >>[ 253.873310] [<ffffffff812a31ec>] ? SYSC_migrate_pages+0xac/0x380 >>[ 253.873310] [<ffffffff811763c6>] ? vtime_account_user+0x96/0xb0 >>[ 253.873310] [<ffffffff812a34ce>] SyS_migrate_pages+0xe/0x10 >>[ 253.873310] [<ffffffff843c4990>] tracesys+0xdd/0xe2 >>[ 253.873310] Code: 0f 1f 00 65 48 ff 04 25 10 25 1d 00 48 83 c4 08 >>5b c9 c3 55 48 89 e5 53 48 83 ec 08 66 66 66 66 90 48 8b 07 48 89 fb >>a8 01 75 10 <0f> 0b 66 0f 1f 44 00 00 eb fe 66 0f 1f 44 00 00 f0 0f ba >>2f 15 >>[ 253.873310] RIP [<ffffffff81281f28>] mlock_vma_page+0x18/0xc0 >>[ 253.873310] RSP <ffff8804d34e99e8> >>[ 253.904194] ---[ end trace be59c4a7f8edab3f ]--- >> >>Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx> >>Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> >>--- >> mm/huge_memory.c | 2 +- >> mm/internal.h | 4 ++-- >> mm/ksm.c | 2 +- >> mm/memory.c | 2 +- >> mm/mlock.c | 5 +++-- >> mm/rmap.c | 4 ++-- >> 6 files changed, 10 insertions(+), 9 deletions(-) >> >>diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>index 33a5dc4..7a15b04 100644 >>--- a/mm/huge_memory.c >>+++ b/mm/huge_memory.c >>@@ -1264,7 +1264,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, >> if (page->mapping && trylock_page(page)) { >> lru_add_drain(); >> if (page->mapping) >>- mlock_vma_page(page); >>+ mlock_vma_page(page, true); >> unlock_page(page); >> } >> } >>diff --git a/mm/internal.h b/mm/internal.h >>index a85a3ab..4ea2d4e 100644 >>--- a/mm/internal.h >>+++ b/mm/internal.h >>@@ -192,7 +192,7 @@ static inline int mlocked_vma_newpage(struct vm_area_struct *vma, >> /* >> * must be called with vma's mmap_sem held for read or write, and page locked. >> */ >>-extern void mlock_vma_page(struct page *page); >>+extern void mlock_vma_page(struct page *page, bool check_page); >> extern unsigned int munlock_vma_page(struct page *page); >> >> /* >>@@ -236,7 +236,7 @@ static inline int mlocked_vma_newpage(struct vm_area_struct *v, struct page *p) >> return 0; >> } >> static inline void clear_page_mlock(struct page *page) { } >>-static inline void mlock_vma_page(struct page *page) { } >>+static inline void mlock_vma_page(struct page *page, bool check_page) { } >> static inline void mlock_migrate_page(struct page *new, struct page *old) { } >> >> #endif /* !CONFIG_MMU */ >>diff --git a/mm/ksm.c b/mm/ksm.c >>index 175fff7..ec36f04 100644 >>--- a/mm/ksm.c >>+++ b/mm/ksm.c >>@@ -1064,7 +1064,7 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, >> if (!PageMlocked(kpage)) { >> unlock_page(page); >> lock_page(kpage); >>- mlock_vma_page(kpage); >>+ mlock_vma_page(kpage, true); >> page = kpage; /* for final unlock */ >> } >> } >>diff --git a/mm/memory.c b/mm/memory.c >>index cf6098c..a41df6a 100644 >>--- a/mm/memory.c >>+++ b/mm/memory.c >>@@ -1602,7 +1602,7 @@ split_fallthrough: >> * know the page is still mapped, we don't even >> * need to check for file-cache page truncation. >> */ >>- mlock_vma_page(page); >>+ mlock_vma_page(page, true); >> unlock_page(page); >> } >> } >>diff --git a/mm/mlock.c b/mm/mlock.c >>index d480cd6..c395ec5 100644 >>--- a/mm/mlock.c >>+++ b/mm/mlock.c >>@@ -77,9 +77,10 @@ void clear_page_mlock(struct page *page) >> * Mark page as mlocked if not already. >> * If page on LRU, isolate and putback to move to unevictable list. >> */ >>-void mlock_vma_page(struct page *page) >>+void mlock_vma_page(struct page *page, bool check_page) >> { >>- BUG_ON(!PageLocked(page)); >>+ if (check_page) >>+ BUG_ON(!PageLocked(page)); >> >> if (!TestSetPageMlocked(page)) { >> mod_zone_page_state(page_zone(page), NR_MLOCK, >>diff --git a/mm/rmap.c b/mm/rmap.c >>index 55c8b8d..79d456f 100644 >>--- a/mm/rmap.c >>+++ b/mm/rmap.c >>@@ -1297,7 +1297,7 @@ out_mlock: >> */ >> if (down_read_trylock(&vma->vm_mm->mmap_sem)) { >> if (vma->vm_flags & VM_LOCKED) { >>- mlock_vma_page(page); >>+ mlock_vma_page(page, true); >> ret = SWAP_MLOCK; >> } >> up_read(&vma->vm_mm->mmap_sem); >>@@ -1385,7 +1385,7 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, >> BUG_ON(!page || PageAnon(page)); >> >> if (locked_vma) { >>- mlock_vma_page(page); /* no-op if already mlocked */ >>+ mlock_vma_page(page, page == check_page); /* no-op if already mlocked */ >> if (page == check_page) >> ret = SWAP_MLOCK; >> continue; /* don't unmap */ >> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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