The 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
The commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault()
codepaths") rework the relevant code but ignore this race. This will
cause the deadlock above to appear again, so fix it.
Fixes: f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths")
Signed-off-by: Qi Zheng <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
CC: <[email protected]>
---
Changelog in v1 -> v2:
- Update commit log
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