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>
diff --git a/mm/mremap.c b/mm/mremap.c
index 7dcf7b4..d3f42be 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -346,6 +346,7 @@
{
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 @@
if (old_len > vma->vm_end - addr)
return ERR_PTR(-EFAULT);
- /* Need to be careful about a growing mapping */
- if (new_len > old_len) {
- unsigned long pgoff;
+ if (new_len == old_len)
+ return vma;
- 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);
- }
+ /* Need to be careful about a growing mapping */
+ 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;