mm: directly use __mlock_vma_pages_range() in find_extend_vma()

In find_extend_vma(), we don't need mlock_vma_pages_range() to verify
the vma type - we know we're working with a stack.  So, we can call
directly into __mlock_vma_pages_range(), and remove the last
make_pages_present() call site.

Note that we don't use mm_populate() here, so we can't release the
mmap_sem while allocating new stack pages.  This is deemed acceptable,
because the stack vmas grow by a bounded number of pages at a time, and
these are anon pages so we don't have to read from disk to populate
them.

Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Tested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Greg Ungerer <gregungerer@westnet.com.au>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 54 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index a296a49865df..569400a5d079 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -155,9 +155,8 @@ void munlock_vma_page(struct page *page)
  *
  * vma->vm_mm->mmap_sem must be held for at least read.
  */
-static long __mlock_vma_pages_range(struct vm_area_struct *vma,
-                                    unsigned long start, unsigned long end,
-                                    int *nonblocking)
+long __mlock_vma_pages_range(struct vm_area_struct *vma,
+                unsigned long start, unsigned long end, int *nonblocking)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long addr = start;
@@ -202,56 +201,6 @@ static int __mlock_posix_error_return(long retval)
         return retval;
 }
 
-/**
- * mlock_vma_pages_range() - mlock pages in specified vma range.
- * @vma - the vma containing the specfied address range
- * @start - starting address in @vma to mlock
- * @end   - end address [+1] in @vma to mlock
- *
- * For mmap()/mremap()/expansion of mlocked vma.
- *
- * return 0 on success for "normal" vmas.
- *
- * return number of pages [> 0] to be removed from locked_vm on success
- * of "special" vmas.
- */
-long mlock_vma_pages_range(struct vm_area_struct *vma,
-                        unsigned long start, unsigned long end)
-{
-        int nr_pages = (end - start) / PAGE_SIZE;
-        BUG_ON(!(vma->vm_flags & VM_LOCKED));
-
-        /*
-         * filter unlockable vmas
-         */
-        if (vma->vm_flags & (VM_IO | VM_PFNMAP))
-                goto no_mlock;
-
-        if (!((vma->vm_flags & VM_DONTEXPAND) ||
-                        is_vm_hugetlb_page(vma) ||
-                        vma == get_gate_vma(current->mm))) {
-
-                __mlock_vma_pages_range(vma, start, end, NULL);
-
-                /* Hide errors from mmap() and other callers */
-                return 0;
-        }
-
-        /*
-         * User mapped kernel pages or huge pages:
-         * make these pages present to populate the ptes, but
-         * fall thru' to reset VM_LOCKED--no need to unlock, and
-         * return nr_pages so these don't get counted against task's
-         * locked limit.  huge pages are already counted against
-         * locked vm limit.
-         */
-        make_pages_present(start, end);
-
-no_mlock:
-        vma->vm_flags &= ~VM_LOCKED;    /* and don't come back! */
-        return nr_pages;                /* error or pages NOT mlocked */
-}
-
 /*
  * munlock_vma_pages_range() - munlock all pages in the vma range.'
  * @vma - vma containing range to be munlock()ed.
@@ -303,7 +252,7 @@ void munlock_vma_pages_range(struct vm_area_struct *vma,
  *
  * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
  * munlock is a no-op.  However, for some special vmas, we go ahead and
- * populate the ptes via make_pages_present().
+ * populate the ptes.
  *
  * For vmas that pass the filters, merge/split as appropriate.
  */