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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-03-17 14:20:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-17 15:09:34 -0700
commit5f7377147ce0b5d521c0ee2aab2ec3ead51297db (patch)
tree4525af234d84b4ff3fe3338ce6faee08630b11f2
parentfec89c109f3a7737fe3a7bf0f40d1fb7709d353b (diff)
thp: fix deadlock in split_huge_pmd()
split_huge_pmd() tries to munlock page with munlock_vma_page(). That requires the page to locked. If the is locked by caller, we would get a deadlock: Unable to find swap-space signature INFO: task trinity-c85:1907 blocked for more than 120 seconds. Not tainted 4.4.0-00032-gf19d0bdced41-dirty #1606 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. trinity-c85 D ffff88084d997608 0 1907 309 0x00000000 Call Trace: schedule+0x9f/0x1c0 schedule_timeout+0x48e/0x600 io_schedule_timeout+0x1c3/0x390 bit_wait_io+0x29/0xd0 __wait_on_bit_lock+0x94/0x140 __lock_page+0x1d4/0x280 __split_huge_pmd+0x5a8/0x10f0 split_huge_pmd_address+0x1d9/0x230 try_to_unmap_one+0x540/0xc70 rmap_walk_anon+0x284/0x810 rmap_walk_locked+0x11e/0x190 try_to_unmap+0x1b1/0x4b0 split_huge_page_to_list+0x49d/0x18a0 follow_page_mask+0xa36/0xea0 SyS_move_pages+0xaf3/0x1570 entry_SYSCALL_64_fastpath+0x12/0x6b 2 locks held by trinity-c85/1907: #0: (&mm->mmap_sem){++++++}, at: SyS_move_pages+0x933/0x1570 #1: (&anon_vma->rwsem){++++..}, at: split_huge_page_to_list+0x402/0x18a0 I don't think the deadlock is triggerable without split_huge_page() simplifilcation patchset. But munlock_vma_page() here is wrong: we want to munlock the page unconditionally, no need in rmap lookup, that munlock_vma_page() does. Let's use clear_page_mlock() instead. It can be called under ptl. Fixes: e90309c9f772 ("thp: allow mlocked THP again") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/huge_memory.c13
1 files changed, 2 insertions, 11 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4a58fa19afac..021db1781872 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2981,29 +2981,20 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
{
spinlock_t *ptl;
struct mm_struct *mm = vma->vm_mm;
- struct page *page = NULL;
unsigned long haddr = address & HPAGE_PMD_MASK;
mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
ptl = pmd_lock(mm, pmd);
if (pmd_trans_huge(*pmd)) {
- page = pmd_page(*pmd);
+ struct page *page = pmd_page(*pmd);
if (PageMlocked(page))
- get_page(page);
- else
- page = NULL;
+ clear_page_mlock(page);
} else if (!pmd_devmap(*pmd))
goto out;
__split_huge_pmd_locked(vma, pmd, haddr, freeze);
out:
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
- if (page) {
- lock_page(page);
- munlock_vma_page(page);
- unlock_page(page);
- put_page(page);
- }
}
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,