mm/mprotect: factor out check whether manual PTE write upgrades are required

Let's factor the check out into vma_wants_manual_pte_write_upgrade(), to be
reused in NUMA hinting fault context soon.

Link: https://lkml.kernel.org/r/20221108174652.198904-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d33639b..e203e8a 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2088,6 +2088,20 @@ extern unsigned long move_page_tables(struct vm_area_struct *vma,
 #define  MM_CP_UFFD_WP_ALL                 (MM_CP_UFFD_WP | \
                                            MM_CP_UFFD_WP_RESOLVE)
 
+int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);
+static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma)
+{
+       /*
+        * We want to check manually if we can change individual PTEs writable
+        * if we can't do that automatically for all PTEs in a mapping. For
+        * private mappings, that's always the case when we have write
+        * permissions as we properly have to handle COW.
+        */
+       if (vma->vm_flags & VM_SHARED)
+               return vma_wants_writenotify(vma, vma->vm_page_prot);
+       return !!(vma->vm_flags & VM_WRITE);
+
+}
 extern unsigned long change_protection(struct mmu_gather *tlb,
                              struct vm_area_struct *vma, unsigned long start,
                              unsigned long end, pgprot_t newprot,
@@ -2227,8 +2241,6 @@ static inline int pte_devmap(pte_t pte)
 }
 #endif
 
-int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);
-
 extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
                               spinlock_t **ptl);
 static inline pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 72aabff..fe22db2 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -558,8 +558,8 @@ mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
        struct mm_struct *mm = vma->vm_mm;
        unsigned long oldflags = vma->vm_flags;
        long nrpages = (end - start) >> PAGE_SHIFT;
+       unsigned int mm_cp_flags = 0;
        unsigned long charged = 0;
-       bool try_change_writable;
        pgoff_t pgoff;
        int error;
 
@@ -637,20 +637,11 @@ success:
         * held in write mode.
         */
        vma->vm_flags = newflags;
-       /*
-        * We want to check manually if we can change individual PTEs writable
-        * if we can't do that automatically for all PTEs in a mapping. For
-        * private mappings, that's always the case when we have write
-        * permissions as we properly have to handle COW.
-        */
-       if (vma->vm_flags & VM_SHARED)
-               try_change_writable = vma_wants_writenotify(vma, vma->vm_page_prot);
-       else
-               try_change_writable = !!(vma->vm_flags & VM_WRITE);
+       if (vma_wants_manual_pte_write_upgrade(vma))
+               mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
        vma_set_page_prot(vma);
 
-       change_protection(tlb, vma, start, end, vma->vm_page_prot,
-                         try_change_writable ? MM_CP_TRY_CHANGE_WRITABLE : 0);
+       change_protection(tlb, vma, start, end, vma->vm_page_prot, mm_cp_flags);
 
        /*
         * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major