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mm: introduce vma_is_anonymous(vma) helper 

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
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>
[bwh: Backported to 3.16 as dependency of "mm/mincore.c: make mincore() more
 conservative"; adjusted context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Oleg Nesterov 2015-09-08 14:58:28 -07:00 committed by syphyr
parent e41eda8e2b
commit 16a37d8853
2 changed files with 9 additions and 3 deletions
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5
include/linux/mm.h
View File

@ -1107,6 +1107,11 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen);
extern pid_t
vm_is_stack(struct task_struct *task, struct vm_area_struct *vma, int in_group);
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,

7
mm/memory.c
View File

@ -3833,11 +3833,12 @@ int handle_pte_fault(struct mm_struct *mm,
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_linear_fault(mm, vma, address,
pte, pmd, flags, entry);
return do_anonymous_page(mm, vma, address,
pte, pmd, flags);
}
if (pte_file(entry))
return do_nonlinear_fault(mm, vma, address,