mm: memory: check userfaultfd_wp() in vmf_orig_pte_uffd_wp()

Add userfaultfd_wp() check in vmf_orig_pte_uffd_wp() to avoid the
unnecessary FAULT_FLAG_ORIG_PTE_VALID check/pte_marker_entry_uffd_wp() in
most pagefault, note, the function vmf_orig_pte_uffd_wp() is not inlined
in the two kernel versions, the difference is shown below,

perf date,

  perf report -i perf.data.before | grep vmf
     0.17%     0.13%  lat_pagefault  [kernel.kallsyms]      [k] vmf_orig_pte_uffd_wp.part.0.isra.0
  perf report -i perf.data.after  | grep vmf

lat_pagefault -W 5 -N 5 /tmp/XXX
  latency              before        after        diff
  average(8 tests)     0.262675      0.2600375   -0.0026375

Although it's a small, but the uffd_wp is a new feature than previous
kernel, when the vma is not registered with UFFD_WP, let's avoid to
execute the new logical, also adding __always_inline attribute to
vmf_orig_pte_uffd_wp(), which make set_pte_range() only check VM_UFFD_WP
flags without the function call.  In addition, directly call the
vmf_orig_pte_uffd_wp() in do_anonymous_page() and set_pte_range() to save
an uffd_wp variable.

Link: https://lkml.kernel.org/r/20240422030039.3293568-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index 9e07d1b9020cb506f60961e9fe897c4d11598fa1..c0bd4e0d5e7a7ccddd58438be245b0de37d5e8a1 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -112,8 +112,10 @@ static bool vmf_pte_changed(struct vm_fault *vmf);
  * Return true if the original pte was a uffd-wp pte marker (so the pte was
  * wr-protected).
  */
-static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
+static __always_inline bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
 {
+       if (!userfaultfd_wp(vmf->vma))
+               return false;
        if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID))
                return false;
 
@@ -4393,7 +4395,6 @@ fallback:
  */
 static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 {
-       bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
        struct vm_area_struct *vma = vmf->vma;
        unsigned long addr = vmf->address;
        struct folio *folio;
@@ -4493,7 +4494,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
        folio_add_new_anon_rmap(folio, vma, addr);
        folio_add_lru_vma(folio, vma);
 setpte:
-       if (uffd_wp)
+       if (vmf_orig_pte_uffd_wp(vmf))
                entry = pte_mkuffd_wp(entry);
        set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr_pages);
 
@@ -4668,7 +4669,6 @@ void set_pte_range(struct vm_fault *vmf, struct folio *folio,
                struct page *page, unsigned int nr, unsigned long addr)
 {
        struct vm_area_struct *vma = vmf->vma;
-       bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
        bool write = vmf->flags & FAULT_FLAG_WRITE;
        bool prefault = in_range(vmf->address, addr, nr * PAGE_SIZE);
        pte_t entry;
@@ -4683,7 +4683,7 @@ void set_pte_range(struct vm_fault *vmf, struct folio *folio,
 
        if (write)
                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-       if (unlikely(uffd_wp))
+       if (unlikely(vmf_orig_pte_uffd_wp(vmf)))
                entry = pte_mkuffd_wp(entry);
        /* copy-on-write page */
        if (write && !(vma->vm_flags & VM_SHARED)) {