/*
 * 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:1102-1120
 * Exact source lines, not a restored book listing or standalone program.
 */
void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	struct page *subpage = page;

	page = compound_head(page);

	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_VMA(!anon_vma, vma);

	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	/*
	 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
	 * simultaneously, so a concurrent reader (eg folio_referenced()'s
	 * folio_test_anon()) will not see one without the other.
	 */
	WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
	SetPageAnonExclusive(subpage);
}