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-rw-r--r--mm/hmm.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
index 601a99ce3c84..6a151c09de5e 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -492,8 +492,21 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
required_fault =
hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
if (required_fault) {
+ int ret;
+
spin_unlock(ptl);
- return hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_unlock_read(vma);
+ /*
+ * Avoid deadlock: drop the vma lock before calling
+ * hmm_vma_fault(), which will itself potentially take and
+ * drop the vma lock. This is also correct from a
+ * protection point of view, because there is no further
+ * use here of either pte or ptl after dropping the vma
+ * lock.
+ */
+ ret = hmm_vma_fault(addr, end, required_fault, walk);
+ hugetlb_vma_lock_read(vma);
+ return ret;
}
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);