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>
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mm/mremap.c
21
mm/mremap.c
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@ -346,6 +346,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
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{
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{
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struct mm_struct *mm = current->mm;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma = find_vma(mm, addr);
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struct vm_area_struct *vma = find_vma(mm, addr);
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unsigned long pgoff;
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if (!vma || vma->vm_start > addr)
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if (!vma || vma->vm_start > addr)
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return ERR_PTR(-EFAULT);
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return ERR_PTR(-EFAULT);
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@ -357,17 +358,17 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
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if (old_len > vma->vm_end - addr)
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if (old_len > vma->vm_end - addr)
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return ERR_PTR(-EFAULT);
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return ERR_PTR(-EFAULT);
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/* Need to be careful about a growing mapping */
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if (new_len == old_len)
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if (new_len > old_len) {
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return vma;
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unsigned long pgoff;
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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/* Need to be careful about a growing mapping */
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return ERR_PTR(-EFAULT);
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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pgoff += vma->vm_pgoff;
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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return ERR_PTR(-EINVAL);
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return ERR_PTR(-EINVAL);
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}
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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return ERR_PTR(-EFAULT);
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if (vma->vm_flags & VM_LOCKED) {
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if (vma->vm_flags & VM_LOCKED) {
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unsigned long locked, lock_limit;
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unsigned long locked, lock_limit;
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