/*
 * mm/rmap.c - physical to virtual reverse mappings
 *
 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
 * Released under the General Public License (GPL).
 *
 * Simple, low overhead reverse mapping scheme.
 * Please try to keep this thing as modular as possible.
 *
 * Provides methods for unmapping each kind of mapped page:
 * the anon methods track anonymous pages, and
 * the file methods track pages belonging to an inode.
 *
 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
 * Contributions by Hugh Dickins 2003, 2004
 */

/*
 * Lock ordering in mm:
 *
 * inode->i_rwsem	(while writing or truncating, not reading or faulting)
 *   mm->mmap_lock
 *     mapping->invalidate_lock (in filemap_fault)
 *       page->flags PG_locked (lock_page)   * (see hugetlbfs below)
 *         hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
 *           mapping->i_mmap_rwsem
 *             hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
 *             anon_vma->rwsem
 *               mm->page_table_lock or pte_lock
 *                 swap_lock (in swap_duplicate, swap_info_get)
 *                   mmlist_lock (in mmput, drain_mmlist and others)
 *                   mapping->private_lock (in block_dirty_folio)
 *                     folio_lock_memcg move_lock (in block_dirty_folio)
 *                       i_pages lock (widely used)
 *                         lruvec->lru_lock (in folio_lruvec_lock_irq)
 *                   inode->i_lock (in set_page_dirty's __mark_inode_dirty)
 *                   bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
 *                     sb_lock (within inode_lock in fs/fs-writeback.c)
 *                     i_pages lock (widely used, in set_page_dirty,
 *                               in arch-dependent flush_dcache_mmap_lock,
 *                               within bdi.wb->list_lock in __sync_single_inode)
 *
 * anon_vma->rwsem,mapping->i_mmap_rwsem   (memory_failure, collect_procs_anon)
 *   ->tasklist_lock
 *     pte map lock
 *
 * * hugetlbfs PageHuge() pages take locks in this order:
 *         mapping->i_mmap_rwsem
 *           hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
 *             page->flags PG_locked (lock_page)
 */

/* Upstream Linux v6.0: mm/rmap.c:395-448
 * Exact source lines, not a restored book listing or standalone program.
 */
void unlink_anon_vmas(struct vm_area_struct *vma)
{
	struct anon_vma_chain *avc, *next;
	struct anon_vma *root = NULL;

	/*
	 * 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;

		root = lock_anon_vma_root(root, anon_vma);
		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);

		/*
		 * Leave empty anon_vmas on the list - we'll need
		 * to free them outside the lock.
		 */
		if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
			anon_vma->parent->num_children--;
			continue;
		}

		list_del(&avc->same_vma);
		anon_vma_chain_free(avc);
	}
	if (vma->anon_vma) {
		vma->anon_vma->num_active_vmas--;

		/*
		 * vma would still be needed after unlink, and anon_vma will be prepared
		 * when handle fault.
		 */
		vma->anon_vma = NULL;
	}
	unlock_anon_vma_root(root);

	/*
	 * 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 write-acquire the anon_vma->root->rwsem.
	 */
	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
		struct anon_vma *anon_vma = avc->anon_vma;

		VM_WARN_ON(anon_vma->num_children);
		VM_WARN_ON(anon_vma->num_active_vmas);
		put_anon_vma(anon_vma);

		list_del(&avc->same_vma);
		anon_vma_chain_free(avc);
	}
}