Move FAULT_FLAG_VMA_LOCK check out of handle_pte_fault(). This should
have a significant performance improvement for mmaped files. Write faults
(on read-only shared pages) still take the mmap lock as we do not want
to audit all the implementations of ->pfn_mkwrite() and ->page_mkwrite().
However write-faults on private mappings are handled under the VMA lock.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/memory.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index ad77ac7f8c9b..20a2e9ed4aeb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3393,6 +3393,11 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
vm_fault_t ret;
pte_unmap_unlock(vmf->pte, vmf->ptl);
+ if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+ vma_end_read(vmf->vma);
+ return VM_FAULT_RETRY;
+ }
+
vmf->flags |= FAULT_FLAG_MKWRITE;
ret = vma->vm_ops->pfn_mkwrite(vmf);
if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))
@@ -3415,6 +3420,12 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf, struct folio *folio)
vm_fault_t tmp;
pte_unmap_unlock(vmf->pte, vmf->ptl);
+ if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
+ folio_put(folio);
+ vma_end_read(vmf->vma);
+ return VM_FAULT_RETRY;
+ }
+
tmp = do_page_mkwrite(vmf, folio);
if (unlikely(!tmp || (tmp &
(VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
@@ -5113,12 +5124,6 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
return do_numa_page(vmf);
- if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vmf->vma)) {
- pte_unmap(vmf->pte);
- vma_end_read(vmf->vma);
- return VM_FAULT_RETRY;
- }
-
spin_lock(vmf->ptl);
entry = vmf->orig_pte;
if (unlikely(!pte_same(ptep_get(vmf->pte), entry))) {
--
2.39.2
