mm: avoid repeated anon_vma lock/unlock sequences in unlink_anon_vmas()

	return -ENOMEM;

}

static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)

void unlink_anon_vmas(struct vm_area_struct *vma)

{

	struct anon_vma *anon_vma = anon_vma_chain->anon_vma;

	int empty;

	struct anon_vma_chain *avc, *next;

	struct anon_vma *root = NULL;

	/* If anon_vma_fork fails, we can get an empty anon_vma_chain. */

	if (!anon_vma)

		return;

	/*

	 * Unlink each anon_vma chained to the VMA.  This list is ordered

	 * from newest to oldest, ensuring the root anon_vma gets freed last.

	 */

	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {

		struct anon_vma *anon_vma = avc->anon_vma;

	anon_vma_lock(anon_vma);

	list_del(&anon_vma_chain->same_anon_vma);

		root = lock_anon_vma_root(root, anon_vma);

		list_del(&avc->same_anon_vma);

	/* We must garbage collect the anon_vma if it's empty */

	empty = list_empty(&anon_vma->head);

	anon_vma_unlock(anon_vma);

		/*

		 * Leave empty anon_vmas on the list - we'll need

		 * to free them outside the lock.

		 */

		if (list_empty(&anon_vma->head))

			continue;

	if (empty)

		put_anon_vma(anon_vma);

		list_del(&avc->same_vma);

		anon_vma_chain_free(avc);

	}

void unlink_anon_vmas(struct vm_area_struct *vma)

{

	struct anon_vma_chain *avc, *next;

	unlock_anon_vma_root(root);

	/*

	 * Unlink each anon_vma chained to the VMA.  This list is ordered

	 * from newest to oldest, ensuring the root anon_vma gets freed last.

	 * Iterate the list once more, it now only contains empty and unlinked

	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()

	 * needing to acquire the anon_vma->root->mutex.

	 */

	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {

		anon_vma_unlink(avc);

		struct anon_vma *anon_vma = avc->anon_vma;

		put_anon_vma(anon_vma);

		list_del(&avc->same_vma);

		anon_vma_chain_free(avc);

	}