[PATCH 1/7] mm: fix the deadlock in finish_fault()
From: Qi Zheng <hidden>
Date: 2021-07-18 04:31:12
Also in:
linux-mm, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
The commit 63f3655f9501(mm, memcg: fix reclaim deadlock with writeback) fix a deadlock bug by pre-allocating the pte page table outside of the page lock, the commit f9ce0be71d1f(mm: Cleanup faultaround and finish_fault() codepaths) rework the relevant code but ignore this race, fix it. Fixes: f9ce0be71d1f(mm: Cleanup faultaround and finish_fault() codepaths) Signed-off-by: Qi Zheng <redacted> --- mm/memory.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index db86558791f1..94a17a9a48ab 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -4026,8 +4026,17 @@ vm_fault_t finish_fault(struct vm_fault *vmf) 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() */
--
2.11.0