mm: mmap: merge vma after call_mmap() if possible

		struct list_head *uf)

{

	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma, *prev;

	struct vm_area_struct *vma, *prev, *merge;

	int error;

	struct rb_node **rb_link, *rb_parent;

	unsigned long charged = 0;

		if (error)

			goto unmap_and_free_vma;

		/* If vm_flags changed after call_mmap(), we should try merge vma again

		 * as we may succeed this time.

		 */

		if (unlikely(vm_flags != vma->vm_flags && prev)) {

			merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags,

				NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX);

			if (merge) {

				fput(file);

				vm_area_free(vma);

				vma = merge;

				/* Update vm_flags and possible addr to pick up the change. We don't

				 * warn here if addr changed as the vma is not linked by vma_link().

				 */

				addr = vma->vm_start;

				vm_flags = vma->vm_flags;

				goto unmap_writable;

			}

		}

		/* Can addr have changed??

		 *

		 * Answer: Yes, several device drivers can do it in their

	vma_link(mm, vma, prev, rb_link, rb_parent);

	/* Once vma denies write, undo our temporary denial count */

	if (file) {

unmap_writable:

		if (vm_flags & VM_SHARED)

			mapping_unmap_writable(file->f_mapping);

		if (vm_flags & VM_DENYWRITE)