Commit 779c1023 authored Jan 15, 2010 by David Howells Committed by Linus Torvalds Jan 16, 2010

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>

parent 1e2ae599

mm/nommu.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -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)