[PATCH 3.16 01/10] mm: introduce vma_is_anonymous(vma) helper

From: Ben Hutchings
Date: Tue Jun 18 2019 - 10:34:49 EST

3.16.69-rc1 review patch. If anyone has any objections, please let me know.


From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit b5330628546616af14ff23075fbf8d4ad91f6e25 upstream.

special_mapping_fault() is absolutely broken. It seems it was always
wrong, but this didn't matter until vdso/vvar started to use more than
one page.

And after this change vma_is_anonymous() becomes really trivial, it
simply checks vm_ops == NULL. However, I do think the helper makes
sense. There are a lot of ->vm_ops != NULL checks, the helper makes the
caller's code more understandable (self-documented) and this is more

This patch (of 3):

Preparation. Add the new simple helper, vma_is_anonymous(vma), and change
handle_pte_fault() to use it. It will have more users.

The name is not accurate, say a hpet_mmap()'ed vma is not anonymous.
Perhaps it should be named vma_has_fault() instead. But it matches the
logic in mmap.c/memory.c (see next changes). "True" just means that a
page fault will use do_anonymous_page().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16 as dependency of "mm/mincore.c: make mincore() more
conservative"; adjusted context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
include/linux/mm.h | 5 +++++
mm/memory.c | 8 ++++----
2 files changed, 9 insertions(+), 4 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1241,6 +1241,11 @@ int get_cmdline(struct task_struct *task

int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t);

+static inline bool vma_is_anonymous(struct vm_area_struct *vma)
+ return !vma->vm_ops;
extern unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len,
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3105,12 +3105,12 @@ static int handle_pte_fault(struct mm_st
entry = *pte;
if (!pte_present(entry)) {
if (pte_none(entry)) {
- if (vma->vm_ops)
+ if (vma_is_anonymous(vma))
+ return do_anonymous_page(mm, vma, address,
+ pte, pmd, flags);
+ else
return do_fault(mm, vma, address, pte,
pmd, flags, entry);
- return do_anonymous_page(mm, vma, address,
- pte, pmd, flags);
return do_swap_page(mm, vma, address,
pte, pmd, flags, entry);