From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: mm/gup: finish consolidating error handling
df06b37ffe5a4 ("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/20181121081402.29641-2-jhubbard@xxxxxxxxxx
Fixes: df06b37ffe5a4 ("mm/gup: cache dev_pagemap while pinning pages")
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/mm/gup.c~mm-gup-finish-consolidating-error-handling
+++ a/mm/gup.c
@@ -702,12 +702,11 @@ static long __get_user_pages(struct task
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;
}
_
