mm: move mm_populate()-related code to mm/gup.c

It's odd that we have populate_vma_page_range() and __mm_populate() in
mm/mlock.c.  It's implementation of generic memory population and mlocking
is one of possible side effect, if VM_LOCKED is set.

__get_user_pages() is core of the implementation.  Let's move the code
into mm/gup.c.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 118 insertions, 0 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 1b114ba9aebf..ca7b607ab671 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -819,6 +819,124 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 EXPORT_SYMBOL(get_user_pages);
 
 /**
+ * populate_vma_page_range() -  populate a range of pages in the vma.
+ * @vma:   target vma
+ * @start: start address
+ * @end:   end address
+ * @nonblocking:
+ *
+ * This takes care of mlocking the pages too if VM_LOCKED is set.
+ *
+ * return 0 on success, negative error code on error.
+ *
+ * vma->vm_mm->mmap_sem must be held.
+ *
+ * If @nonblocking is NULL, it may be held for read or write and will
+ * be unperturbed.
+ *
+ * If @nonblocking is non-NULL, it must held for read only and may be
+ * released.  If it's released, *@nonblocking will be set to 0.
+ */
+long populate_vma_page_range(struct vm_area_struct *vma,
+                unsigned long start, unsigned long end, int *nonblocking)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        unsigned long nr_pages = (end - start) / PAGE_SIZE;
+        int gup_flags;
+
+        VM_BUG_ON(start & ~PAGE_MASK);
+        VM_BUG_ON(end   & ~PAGE_MASK);
+        VM_BUG_ON_VMA(start < vma->vm_start, vma);
+        VM_BUG_ON_VMA(end   > vma->vm_end, vma);
+        VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
+
+        gup_flags = FOLL_TOUCH | FOLL_POPULATE;
+        /*
+         * We want to touch writable mappings with a write fault in order
+         * to break COW, except for shared mappings because these don't COW
+         * and we would not want to dirty them for nothing.
+         */
+        if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
+                gup_flags |= FOLL_WRITE;
+
+        /*
+         * We want mlock to succeed for regions that have any permissions
+         * other than PROT_NONE.
+         */
+        if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
+                gup_flags |= FOLL_FORCE;
+
+        /*
+         * We made sure addr is within a VMA, so the following will
+         * not result in a stack expansion that recurses back here.
+         */
+        return __get_user_pages(current, mm, start, nr_pages, gup_flags,
+                                NULL, NULL, nonblocking);
+}
+
+/*
+ * __mm_populate - populate and/or mlock pages within a range of address space.
+ *
+ * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
+ * flags. VMAs must be already marked with the desired vm_flags, and
+ * mmap_sem must not be held.
+ */
+int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
+{
+        struct mm_struct *mm = current->mm;
+        unsigned long end, nstart, nend;
+        struct vm_area_struct *vma = NULL;
+        int locked = 0;
+        long ret = 0;
+
+        VM_BUG_ON(start & ~PAGE_MASK);
+        VM_BUG_ON(len != PAGE_ALIGN(len));
+        end = start + len;
+
+        for (nstart = start; nstart < end; nstart = nend) {
+                /*
+                 * We want to fault in pages for [nstart; end) address range.
+                 * Find first corresponding VMA.
+                 */
+                if (!locked) {
+                        locked = 1;
+                        down_read(&mm->mmap_sem);
+                        vma = find_vma(mm, nstart);
+                } else if (nstart >= vma->vm_end)
+                        vma = vma->vm_next;
+                if (!vma || vma->vm_start >= end)
+                        break;
+                /*
+                 * Set [nstart; nend) to intersection of desired address
+                 * range with the first VMA. Also, skip undesirable VMA types.
+                 */
+                nend = min(end, vma->vm_end);
+                if (vma->vm_flags & (VM_IO | VM_PFNMAP))
+                        continue;
+                if (nstart < vma->vm_start)
+                        nstart = vma->vm_start;
+                /*
+                 * Now fault in a range of pages. populate_vma_page_range()
+                 * double checks the vma flags, so that it won't mlock pages
+                 * if the vma was already munlocked.
+                 */
+                ret = populate_vma_page_range(vma, nstart, nend, &locked);
+                if (ret < 0) {
+                        if (ignore_errors) {
+                                ret = 0;
+                                continue;       /* continue at next VMA */
+                        }
+                        break;
+                }
+                nend = nstart + ret * PAGE_SIZE;
+                ret = 0;
+        }
+        if (locked)
+                up_read(&mm->mmap_sem);
+        return ret;     /* 0 or negative error code */
+}
+
+/**
  * get_dump_page() - pin user page in memory while writing it to core dump
  * @addr: user address
  *