mptcp: simplify subflow_syn_recv_sock()

[linux.git] / mm / hmm.c

diff --git a/mm/hmm.c b/mm/hmm.c
index 601a99ce3c84dba14466bc14f6b5273de9361f17..6a151c09de5eed6743cd96afc24bd5e940dd24bf 100644 (file)
--- 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);