revert "mm: make sure all file VMAs have ->vm_ops set"

Revert commit 6dc296e7df4c "mm: make sure all file VMAs have ->vm_ops
set".

Will Deacon reports that it "causes some mmap regressions in LTP, which
appears to use a MAP_PRIVATE mmap of /dev/zero as a way to get anonymous
pages in some of its tests (specifically mmap10 [1])".

William Shuman reports Oracle crashes.

So revert the patch while we work out what to do.

Reported-by: William Shuman <wshuman3@gmail.com>
Reported-by: Will Deacon <will.deacon@arm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index 971dd2c..c739d6d 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -612,8 +612,6 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm,
 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
                struct rb_node **rb_link, struct rb_node *rb_parent)
 {
-       WARN_ONCE(vma->vm_file && !vma->vm_ops, "missing vma->vm_ops");
-
        /* Update tracking information for the gap following the new vma. */
        if (vma->vm_next)
                vma_gap_update(vma->vm_next);
@@ -1638,12 +1636,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
                 */
                WARN_ON_ONCE(addr != vma->vm_start);
 
-               /* All file mapping must have ->vm_ops set */
-               if (!vma->vm_ops) {
-                       static const struct vm_operations_struct dummy_ops = {};
-                       vma->vm_ops = &dummy_ops;
-               }
-
                addr = vma->vm_start;
                vm_flags = vma->vm_flags;
        } else if (vm_flags & VM_SHARED) {