mm/gup: finish consolidating error handling

Commit df06b37ffe5a ("mm/gup: cache dev_pagemap while pinning pages")
attempted to operate on each page that get_user_pages had retrieved.  In
order to do that, it created a common exit point from the routine.
However, one case was missed, which this patch fixes up.

Also, there was still an unnecessary shadow declaration (with a
different type) of the "ret" variable, which this patch removes.

Keith's description of the situation is:

  This also fixes a potentially leaked dev_pagemap reference count if a
  failure occurs when an iteration crosses a vma boundary.  I don't think
  it's normal to have different vma's on a users mapped zone device
  memory, but good to fix anyway.

I actually thought that this code:

    /* first iteration or cross vma bound */
    if (!vma || start >= vma->vm_end) {
	        vma = find_extend_vma(mm, start);
	        if (!vma && in_gate_area(mm, start)) {
		            ret = get_gate_page(mm, start & PAGE_MASK,
		                    gup_flags, &vma,
		                    pages ? &pages[i] : NULL);
		            if (ret)
		                goto out;

dealt with the "you're trying to pin the gate page, as part of this
call", rather than the generic case of crossing a vma boundary.  (I
think there's a fine point that I must be overlooking.) But it's still a
valid case, either way.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: df06b37ffe5a4 ("mm/gup: cache dev_pagemap while pinning pages")
Signed-off-by: John Hubbard <[email protected]>
Reviewed-by: Keith Busch <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Dave Hansen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/gup.c b/mm/gup.c
index aa43620a3270ec08040f75e587d4cbe7617754ff..8cb68a50dbdf28a27dfaef6dce27e6cdb1f87881 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -702,12 +702,11 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                if (!vma || start >= vma->vm_end) {
                        vma = find_extend_vma(mm, start);
                        if (!vma && in_gate_area(mm, start)) {
-                               int ret;
                                ret = get_gate_page(mm, start & PAGE_MASK,
                                                gup_flags, &vma,
                                                pages ? &pages[i] : NULL);
                                if (ret)
-                                       return i ? : ret;
+                                       goto out;
                                ctx.page_mask = 0;
                                goto next_page;
                        }