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authorOleg Nesterov <oleg@redhat.com>2015-09-04 15:48:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-04 16:54:41 -0700
commit1d3916869798755968b3cd764ab21f2bb86ffff7 (patch)
treed8a9baa17fab65069a49000cfe4c741982f1ccfe
parentd456fb9e5254df433d4806769d7ff75d80d66aa4 (diff)
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mremap: don't do uneccesary checks if new_len == old_len
The "new_len > old_len" branch in vma_to_resize() looks very confusing. It only covers the VM_DONTEXPAND/pgoff checks but everything below is equally unneeded if new_len == old_len. Change this code to return if "new_len == old_len", new_len < old_len is not possible, otherwise the code below is wrong anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Laurent Dufour <ldufour@linux.vnet.ibm.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>
-rw-r--r--mm/mremap.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 7dcf7b42068e..d3f42bece564 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -346,6 +346,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = find_vma(mm, addr);
+ unsigned long pgoff;
if (!vma || vma->vm_start > addr)
return ERR_PTR(-EFAULT);
@@ -357,17 +358,17 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
if (old_len > vma->vm_end - addr)
return ERR_PTR(-EFAULT);
+ if (new_len == old_len)
+ return vma;
+
/* Need to be careful about a growing mapping */
- if (new_len > old_len) {
- unsigned long pgoff;
-
- if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
- return ERR_PTR(-EFAULT);
- pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
- pgoff += vma->vm_pgoff;
- if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
- return ERR_PTR(-EINVAL);
- }
+ pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
+ pgoff += vma->vm_pgoff;
+ if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
+ return ERR_PTR(-EINVAL);
+
+ if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
+ return ERR_PTR(-EFAULT);
if (vma->vm_flags & VM_LOCKED) {
unsigned long locked, lock_limit;