diff options
| author | David Howells <dhowells@redhat.com> | 2010-01-15 17:01:34 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-01-16 12:15:40 -0800 |
| commit | 779c10232ceb11c1b259232c4845cfb2850287b7 (patch) | |
| tree | 972b07acdcff03b20c84d42425a64b231df52aaa /mm/nommu.c | |
| parent | 1e2ae599d37e60958c03ca5e46b1f657619a30cd (diff) | |
| download | lwn-779c10232ceb11c1b259232c4845cfb2850287b7.tar.gz lwn-779c10232ceb11c1b259232c4845cfb2850287b7.zip | |
nommu: remove a superfluous check of vm_region::vm_usage
In split_vma(), there's no need to check if the VMA being split has a
region that's in use by more than one VMA because:
(1) The preceding test prohibits splitting of non-anonymous VMAs and regions
(eg: file or chardev backed VMAs).
(2) Anonymous regions can't be mapped multiple times because there's no handle
by which to refer to the already existing region.
(3) If a VMA has previously been split, then the region backing it has also
been split into two regions, each of usage 1.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/nommu.c')
| -rw-r--r-- | mm/nommu.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/nommu.c b/mm/nommu.c index 5e39294f8ea8..d6dd656264a2 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1441,10 +1441,9 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, kenter(""); - /* we're only permitted to split anonymous regions that have a single - * owner */ - if (vma->vm_file || - vma->vm_region->vm_usage != 1) + /* we're only permitted to split anonymous regions (these should have + * only a single usage on the region) */ + if (vma->vm_file) return -ENOMEM; if (mm->map_count >= sysctl_max_map_count) |