| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.13 201/223] mm: fix the deadlock in finish_fault() | Date | Mon, 26 Jul 2021 17:39:53 +0200 |
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From: Qi Zheng <zhengqi.arch@bytedance.com>
commit e4dc3489143f84f7ed30be58b886bb6772f229b9 upstream.
Commit 63f3655f9501 ("mm, memcg: fix reclaim deadlock with writeback") fix the following ABBA deadlock by pre-allocating the pte page table without holding the page lock.
lock_page(A) SetPageWriteback(A) unlock_page(A) lock_page(B) lock_page(B) pte_alloc_one shrink_page_list wait_on_page_writeback(A) SetPageWriteback(B) unlock_page(B)
# flush A, B to clear the writeback
Commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") reworked the relevant code but ignored this race. This will cause the deadlock above to appear again, so fix it.
Link: https://lkml.kernel.org/r/20210721074849.57004-1-zhengqi.arch@bytedance.com Fixes: f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- mm/memory.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
--- a/mm/memory.c +++ b/mm/memory.c @@ -3891,8 +3891,17 @@ vm_fault_t finish_fault(struct vm_fault return ret; } - if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd))) + if (vmf->prealloc_pte) { + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); + if (likely(pmd_none(*vmf->pmd))) { + mm_inc_nr_ptes(vma->vm_mm); + pmd_populate(vma->vm_mm, vmf->pmd, vmf->prealloc_pte); + vmf->prealloc_pte = NULL; + } + spin_unlock(vmf->ptl); + } else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd))) { return VM_FAULT_OOM; + } } /* See comment in handle_pte_fault() */
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