On 11/03/2020 18:35, Jason Gunthorpe wrote:
From: Jason Gunthorpe <j...@mellanox.com>

This eventually calls into handle_mm_fault() which is a sleeping function.
Release the lock first.

hmm_vma_walk_hole() does not touch the contents of the PUD, so it does not
need the lock.

Fixes: 3afc423632a1 ("mm: pagewalk: add p4d_entry() and pgd_entry()")
Cc: Steven Price <steven.pr...@arm.com>
Signed-off-by: Jason Gunthorpe <j...@mellanox.com>

Sorry about that, thanks for fixing.

Reviewed-by: Steven Price <steven.pr...@arm.com>

---
  mm/hmm.c | 14 +++++++-------
  1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 9e8f68eb83287a..32dcbfd3908315 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -473,8 +473,8 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long 
start, unsigned long end,
pud = READ_ONCE(*pudp);
        if (pud_none(pud)) {
-               ret = hmm_vma_walk_hole(start, end, -1, walk);
-               goto out_unlock;
+               spin_unlock(ptl);
+               return hmm_vma_walk_hole(start, end, -1, walk);
        }
if (pud_huge(pud) && pud_devmap(pud)) {
@@ -483,8 +483,8 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long 
start, unsigned long end,
                bool fault, write_fault;
if (!pud_present(pud)) {
-                       ret = hmm_vma_walk_hole(start, end, -1, walk);
-                       goto out_unlock;
+                       spin_unlock(ptl);
+                       return hmm_vma_walk_hole(start, end, -1, walk);
                }
i = (addr - range->start) >> PAGE_SHIFT;
@@ -495,9 +495,9 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long 
start, unsigned long end,
                hmm_range_need_fault(hmm_vma_walk, pfns, npages,
                                     cpu_flags, &fault, &write_fault);
                if (fault || write_fault) {
-                       ret = hmm_vma_walk_hole_(addr, end, fault,
-                                                write_fault, walk);
-                       goto out_unlock;
+                       spin_unlock(ptl);
+                       return hmm_vma_walk_hole_(addr, end, fault, write_fault,
+                                                 walk);
                }
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);


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