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: e90309c9f7
("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>
This commit is contained in:
Родитель
fec89c109f
Коммит
5f7377147c
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@ -2981,29 +2981,20 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
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{
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spinlock_t *ptl;
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struct mm_struct *mm = vma->vm_mm;
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struct page *page = NULL;
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unsigned long haddr = address & HPAGE_PMD_MASK;
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mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
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ptl = pmd_lock(mm, pmd);
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if (pmd_trans_huge(*pmd)) {
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page = pmd_page(*pmd);
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struct page *page = pmd_page(*pmd);
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if (PageMlocked(page))
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get_page(page);
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else
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page = NULL;
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clear_page_mlock(page);
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} else if (!pmd_devmap(*pmd))
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goto out;
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__split_huge_pmd_locked(vma, pmd, haddr, freeze);
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out:
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spin_unlock(ptl);
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mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
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if (page) {
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lock_page(page);
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munlock_vma_page(page);
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unlock_page(page);
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put_page(page);
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}
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}
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void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
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