From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Subject: mm: fix the deadlock in finish_fault()
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") rework the relevant code but ignore 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@xxxxxxxxxxxxx
Fixes: f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths")
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/mm/memory.c~mm-fix-the-deadlock-in-finish_fault
+++ a/mm/memory.c
@@ -4026,8 +4026,17 @@ 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() */
_
