The fault path will immediately fail in handle_mm_fault(), so this
is the minimal step which allows the per-VMA lock to be taken on
file-backed VMAs. There may be a small performance reduction as a
little unnecessary work will be done on each page fault. See later
patches for the improvement.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/memory.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 2c7967632866..f2dcc695f54e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5247,6 +5247,11 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
goto out;
}
+ if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) {
+ vma_end_read(vma);
+ return VM_FAULT_RETRY;
+ }
+
/*
* Enable the memcg OOM handling for faults triggered in user
* space. Kernel faults are handled more gracefully.
@@ -5418,12 +5423,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
if (!vma)
goto inval;
- /* Only anonymous vmas are supported for now */
- if (!vma_is_anonymous(vma))
- goto inval;
-
/* find_mergeable_anon_vma uses adjacent vmas which are not locked */
- if (!vma->anon_vma)
+ if (vma_is_anonymous(vma) && !vma->anon_vma)
goto inval;
if (!vma_start_read(vma))
--
2.39.2
