Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH 3/6] NOMMU: Remove a superfluous check of vm_region::vm_usage | Date | Thu, 14 Jan 2010 13:58:40 +0000 |
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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> ---
mm/nommu.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c index 5e39294..d6dd656 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)
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