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mm: introduce vma_is_anonymous(vma) helper 

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
grep-friendly.

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@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2015-09-08 14:58:28 -07:00 committed by Linus Torvalds
parent af8713b701
commit b533062854
2 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/mm.h
View File

@ -1260,6 +1260,11 @@ static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
}
static inline bool vma_is_anonymous(struct vm_area_struct *vma)
{
return !vma->vm_ops;
}
static inline int stack_guard_page_start(struct vm_area_struct *vma,
unsigned long addr)
{

8
mm/memory.c
View File

@ -3267,12 +3267,12 @@ static int handle_pte_fault(struct mm_struct *mm,
barrier();
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);