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nommu: remove a superfluous check of vm_region::vm_usage

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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>
This commit is contained in:
David Howells
2010-01-15 17:01:34 -08:00
committed by Linus Torvalds
parent 1e2ae599d3
commit 779c10232c
1 changed files with 3 additions and 4 deletions
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7
mm/nommu.c
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@@ -1441,10 +1441,9 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
kenter(""); kenter("");
/* we're only permitted to split anonymous regions that have a single /* we're only permitted to split anonymous regions (these should have
* owner */ * only a single usage on the region) */
if (vma->vm_file || if (vma->vm_file)
vma->vm_region->vm_usage != 1)
return -ENOMEM; return -ENOMEM;
if (mm->map_count >= sysctl_max_map_count) if (mm->map_count >= sysctl_max_map_count)