page cache: use xa_lock

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.

[willy@infradead.org: fix nds32, fs/dax.c]
  Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

13 files changed, 176 insertions, 185 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 693f62212a59..ab77e19ab09c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -66,7 +66,7 @@
  *  ->i_mmap_rwsem		(truncate_pagecache)
  *    ->private_lock		(__free_pte->__set_page_dirty_buffers)
  *      ->swap_lock		(exclusive_swap_page, others)
- *        ->mapping->tree_lock
+ *        ->i_pages lock
  *
  *  ->i_mutex
  *    ->i_mmap_rwsem		(truncate->unmap_mapping_range)
@@ -74,7 +74,7 @@
  *  ->mmap_sem
  *    ->i_mmap_rwsem
  *      ->page_table_lock or pte_lock	(various, mainly in memory.c)
- *        ->mapping->tree_lock	(arch-dependent flush_dcache_mmap_lock)
+ *        ->i_pages lock	(arch-dependent flush_dcache_mmap_lock)
  *
  *  ->mmap_sem
  *    ->lock_page		(access_process_vm)
@@ -84,7 +84,7 @@
  *
  *  bdi->wb.list_lock
  *    sb_lock			(fs/fs-writeback.c)
- *    ->mapping->tree_lock	(__sync_single_inode)
+ *    ->i_pages lock		(__sync_single_inode)
  *
  *  ->i_mmap_rwsem
  *    ->anon_vma.lock		(vma_adjust)
@@ -95,11 +95,11 @@
  *  ->page_table_lock or pte_lock
  *    ->swap_lock		(try_to_unmap_one)
  *    ->private_lock		(try_to_unmap_one)
- *    ->tree_lock		(try_to_unmap_one)
+ *    ->i_pages lock		(try_to_unmap_one)
  *    ->zone_lru_lock(zone)	(follow_page->mark_page_accessed)
  *    ->zone_lru_lock(zone)	(check_pte_range->isolate_lru_page)
  *    ->private_lock		(page_remove_rmap->set_page_dirty)
- *    ->tree_lock		(page_remove_rmap->set_page_dirty)
+ *    ->i_pages lock		(page_remove_rmap->set_page_dirty)
  *    bdi.wb->list_lock		(page_remove_rmap->set_page_dirty)
  *    ->inode->i_lock		(page_remove_rmap->set_page_dirty)
  *    ->memcg->move_lock	(page_remove_rmap->lock_page_memcg)
@@ -118,14 +118,15 @@ static int page_cache_tree_insert(struct address_space *mapping,
 	void **slot;
 	int error;
 
-	error = __radix_tree_create(&mapping->page_tree, page->index, 0,
+	error = __radix_tree_create(&mapping->i_pages, page->index, 0,
 				    &node, &slot);
 	if (error)
 		return error;
 	if (*slot) {
 		void *p;
 
-		p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
+		p = radix_tree_deref_slot_protected(slot,
+						    &mapping->i_pages.xa_lock);
 		if (!radix_tree_exceptional_entry(p))
 			return -EEXIST;
 
@@ -133,7 +134,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		if (shadowp)
 			*shadowp = p;
 	}
-	__radix_tree_replace(&mapping->page_tree, node, slot, page,
+	__radix_tree_replace(&mapping->i_pages, node, slot, page,
 			     workingset_lookup_update(mapping));
 	mapping->nrpages++;
 	return 0;
@@ -155,13 +156,13 @@ static void page_cache_tree_delete(struct address_space *mapping,
 		struct radix_tree_node *node;
 		void **slot;
 
-		__radix_tree_lookup(&mapping->page_tree, page->index + i,
+		__radix_tree_lookup(&mapping->i_pages, page->index + i,
 				    &node, &slot);
 
 		VM_BUG_ON_PAGE(!node && nr != 1, page);
 
-		radix_tree_clear_tags(&mapping->page_tree, node, slot);
-		__radix_tree_replace(&mapping->page_tree, node, slot, shadow,
+		radix_tree_clear_tags(&mapping->i_pages, node, slot);
+		__radix_tree_replace(&mapping->i_pages, node, slot, shadow,
 				workingset_lookup_update(mapping));
 	}
 
@@ -253,7 +254,7 @@ static void unaccount_page_cache_page(struct address_space *mapping,
 /*
  * Delete a page from the page cache and free it. Caller has to make
  * sure the page is locked and that nobody else uses it - or that usage
- * is safe.  The caller must hold the mapping's tree_lock.
+ * is safe.  The caller must hold the i_pages lock.
  */
 void __delete_from_page_cache(struct page *page, void *shadow)
 {
@@ -296,9 +297,9 @@ void delete_from_page_cache(struct page *page)
 	unsigned long flags;
 
 	BUG_ON(!PageLocked(page));
-	spin_lock_irqsave(&mapping->tree_lock, flags);
+	xa_lock_irqsave(&mapping->i_pages, flags);
 	__delete_from_page_cache(page, NULL);
-	spin_unlock_irqrestore(&mapping->tree_lock, flags);
+	xa_unlock_irqrestore(&mapping->i_pages, flags);
 
 	page_cache_free_page(mapping, page);
 }
@@ -309,14 +310,14 @@ EXPORT_SYMBOL(delete_from_page_cache);
  * @mapping: the mapping to which pages belong
  * @pvec: pagevec with pages to delete
  *
- * The function walks over mapping->page_tree and removes pages passed in @pvec
- * from the radix tree. The function expects @pvec to be sorted by page index.
- * It tolerates holes in @pvec (radix tree entries at those indices are not
+ * The function walks over mapping->i_pages and removes pages passed in @pvec
+ * from the mapping. The function expects @pvec to be sorted by page index.
+ * It tolerates holes in @pvec (mapping entries at those indices are not
  * modified). The function expects only THP head pages to be present in the
- * @pvec and takes care to delete all corresponding tail pages from the radix
- * tree as well.
+ * @pvec and takes care to delete all corresponding tail pages from the
+ * mapping as well.
  *
- * The function expects mapping->tree_lock to be held.
+ * The function expects the i_pages lock to be held.
  */
 static void
 page_cache_tree_delete_batch(struct address_space *mapping,
@@ -330,11 +331,11 @@ page_cache_tree_delete_batch(struct address_space *mapping,
 	pgoff_t start;
 
 	start = pvec->pages[0]->index;
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
 		if (i >= pagevec_count(pvec) && !tail_pages)
 			break;
 		page = radix_tree_deref_slot_protected(slot,
-						       &mapping->tree_lock);
+						       &mapping->i_pages.xa_lock);
 		if (radix_tree_exceptional_entry(page))
 			continue;
 		if (!tail_pages) {
@@ -357,8 +358,8 @@ page_cache_tree_delete_batch(struct address_space *mapping,
 		} else {
 			tail_pages--;
 		}
-		radix_tree_clear_tags(&mapping->page_tree, iter.node, slot);
-		__radix_tree_replace(&mapping->page_tree, iter.node, slot, NULL,
+		radix_tree_clear_tags(&mapping->i_pages, iter.node, slot);
+		__radix_tree_replace(&mapping->i_pages, iter.node, slot, NULL,
 				workingset_lookup_update(mapping));
 		total_pages++;
 	}
@@ -374,14 +375,14 @@ void delete_from_page_cache_batch(struct address_space *mapping,
 	if (!pagevec_count(pvec))
 		return;
 
-	spin_lock_irqsave(&mapping->tree_lock, flags);
+	xa_lock_irqsave(&mapping->i_pages, flags);
 	for (i = 0; i < pagevec_count(pvec); i++) {
 		trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
 
 		unaccount_page_cache_page(mapping, pvec->pages[i]);
 	}
 	page_cache_tree_delete_batch(mapping, pvec);
-	spin_unlock_irqrestore(&mapping->tree_lock, flags);
+	xa_unlock_irqrestore(&mapping->i_pages, flags);
 
 	for (i = 0; i < pagevec_count(pvec); i++)
 		page_cache_free_page(mapping, pvec->pages[i]);
@@ -798,7 +799,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 		new->mapping = mapping;
 		new->index = offset;
 
-		spin_lock_irqsave(&mapping->tree_lock, flags);
+		xa_lock_irqsave(&mapping->i_pages, flags);
 		__delete_from_page_cache(old, NULL);
 		error = page_cache_tree_insert(mapping, new, NULL);
 		BUG_ON(error);
@@ -810,7 +811,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 			__inc_node_page_state(new, NR_FILE_PAGES);
 		if (PageSwapBacked(new))
 			__inc_node_page_state(new, NR_SHMEM);
-		spin_unlock_irqrestore(&mapping->tree_lock, flags);
+		xa_unlock_irqrestore(&mapping->i_pages, flags);
 		mem_cgroup_migrate(old, new);
 		radix_tree_preload_end();
 		if (freepage)
@@ -852,7 +853,7 @@ static int __add_to_page_cache_locked(struct page *page,
 	page->mapping = mapping;
 	page->index = offset;
 
-	spin_lock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_pages);
 	error = page_cache_tree_insert(mapping, page, shadowp);
 	radix_tree_preload_end();
 	if (unlikely(error))
@@ -861,7 +862,7 @@ static int __add_to_page_cache_locked(struct page *page,
 	/* hugetlb pages do not participate in page cache accounting. */
 	if (!huge)
 		__inc_node_page_state(page, NR_FILE_PAGES);
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 	if (!huge)
 		mem_cgroup_commit_charge(page, memcg, false, false);
 	trace_mm_filemap_add_to_page_cache(page);
@@ -869,7 +870,7 @@ static int __add_to_page_cache_locked(struct page *page,
 err_insert:
 	page->mapping = NULL;
 	/* Leave page->index set: truncation relies upon it */
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 	if (!huge)
 		mem_cgroup_cancel_charge(page, memcg, false);
 	put_page(page);
@@ -1353,7 +1354,7 @@ pgoff_t page_cache_next_hole(struct address_space *mapping,
 	for (i = 0; i < max_scan; i++) {
 		struct page *page;
 
-		page = radix_tree_lookup(&mapping->page_tree, index);
+		page = radix_tree_lookup(&mapping->i_pages, index);
 		if (!page || radix_tree_exceptional_entry(page))
 			break;
 		index++;
@@ -1394,7 +1395,7 @@ pgoff_t page_cache_prev_hole(struct address_space *mapping,
 	for (i = 0; i < max_scan; i++) {
 		struct page *page;
 
-		page = radix_tree_lookup(&mapping->page_tree, index);
+		page = radix_tree_lookup(&mapping->i_pages, index);
 		if (!page || radix_tree_exceptional_entry(page))
 			break;
 		index--;
@@ -1427,7 +1428,7 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 	rcu_read_lock();
 repeat:
 	page = NULL;
-	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
+	pagep = radix_tree_lookup_slot(&mapping->i_pages, offset);
 	if (pagep) {
 		page = radix_tree_deref_slot(pagep);
 		if (unlikely(!page))
@@ -1633,7 +1634,7 @@ unsigned find_get_entries(struct address_space *mapping,
 		return 0;
 
 	rcu_read_lock();
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
 		struct page *head, *page;
 repeat:
 		page = radix_tree_deref_slot(slot);
@@ -1710,7 +1711,7 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
 		return 0;
 
 	rcu_read_lock();
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, *start) {
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, *start) {
 		struct page *head, *page;
 
 		if (iter.index > end)
@@ -1795,7 +1796,7 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
 		return 0;
 
 	rcu_read_lock();
-	radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
+	radix_tree_for_each_contig(slot, &mapping->i_pages, &iter, index) {
 		struct page *head, *page;
 repeat:
 		page = radix_tree_deref_slot(slot);
@@ -1875,8 +1876,7 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
 		return 0;
 
 	rcu_read_lock();
-	radix_tree_for_each_tagged(slot, &mapping->page_tree,
-				   &iter, *index, tag) {
+	radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, *index, tag) {
 		struct page *head, *page;
 
 		if (iter.index > end)
@@ -1969,8 +1969,7 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
 		return 0;
 
 	rcu_read_lock();
-	radix_tree_for_each_tagged(slot, &mapping->page_tree,
-				   &iter, start, tag) {
+	radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start, tag) {
 		struct page *head, *page;
 repeat:
 		page = radix_tree_deref_slot(slot);
@@ -2624,8 +2623,7 @@ void filemap_map_pages(struct vm_fault *vmf,
 	struct page *head, *page;
 
 	rcu_read_lock();
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
-			start_pgoff) {
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start_pgoff) {
 		if (iter.index > end_pgoff)
 			break;
 repeat:
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3f3267af4e3b..14ed6ee5e02f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2450,7 +2450,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	} else {
 		/* Additional pin to radix tree */
 		page_ref_add(head, 2);
-		spin_unlock(&head->mapping->tree_lock);
+		xa_unlock(&head->mapping->i_pages);
 	}
 
 	spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
@@ -2658,15 +2658,15 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 	if (mapping) {
 		void **pslot;
 
-		spin_lock(&mapping->tree_lock);
-		pslot = radix_tree_lookup_slot(&mapping->page_tree,
+		xa_lock(&mapping->i_pages);
+		pslot = radix_tree_lookup_slot(&mapping->i_pages,
 				page_index(head));
 		/*
 		 * Check if the head page is present in radix tree.
 		 * We assume all tail are present too, if head is there.
 		 */
 		if (radix_tree_deref_slot_protected(pslot,
-					&mapping->tree_lock) != head)
+					&mapping->i_pages.xa_lock) != head)
 			goto fail;
 	}
 
@@ -2700,7 +2700,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 		}
 		spin_unlock(&pgdata->split_queue_lock);
 fail:		if (mapping)
-			spin_unlock(&mapping->tree_lock);
+			xa_unlock(&mapping->i_pages);
 		spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
 		unfreeze_page(head);
 		ret = -EBUSY;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index eb32d0707c80..d7b2a4bf8671 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1344,8 +1344,8 @@ static void collapse_shmem(struct mm_struct *mm,
 	 */
 
 	index = start;
-	spin_lock_irq(&mapping->tree_lock);
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
+	xa_lock_irq(&mapping->i_pages);
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
 		int n = min(iter.index, end) - index;
 
 		/*
@@ -1358,7 +1358,7 @@ static void collapse_shmem(struct mm_struct *mm,
 		}
 		nr_none += n;
 		for (; index < min(iter.index, end); index++) {
-			radix_tree_insert(&mapping->page_tree, index,
+			radix_tree_insert(&mapping->i_pages, index,
 					new_page + (index % HPAGE_PMD_NR));
 		}
 
@@ -1367,16 +1367,16 @@ static void collapse_shmem(struct mm_struct *mm,
 			break;
 
 		page = radix_tree_deref_slot_protected(slot,
-				&mapping->tree_lock);
+				&mapping->i_pages.xa_lock);
 		if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
-			spin_unlock_irq(&mapping->tree_lock);
+			xa_unlock_irq(&mapping->i_pages);
 			/* swap in or instantiate fallocated page */
 			if (shmem_getpage(mapping->host, index, &page,
 						SGP_NOHUGE)) {
 				result = SCAN_FAIL;
 				goto tree_unlocked;
 			}
-			spin_lock_irq(&mapping->tree_lock);
+			xa_lock_irq(&mapping->i_pages);
 		} else if (trylock_page(page)) {
 			get_page(page);
 		} else {
@@ -1385,7 +1385,7 @@ static void collapse_shmem(struct mm_struct *mm,
 		}
 
 		/*
-		 * The page must be locked, so we can drop the tree_lock
+		 * The page must be locked, so we can drop the i_pages lock
 		 * without racing with truncate.
 		 */
 		VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -1396,7 +1396,7 @@ static void collapse_shmem(struct mm_struct *mm,
 			result = SCAN_TRUNCATED;
 			goto out_unlock;
 		}
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 
 		if (isolate_lru_page(page)) {
 			result = SCAN_DEL_PAGE_LRU;
@@ -1406,11 +1406,11 @@ static void collapse_shmem(struct mm_struct *mm,
 		if (page_mapped(page))
 			unmap_mapping_pages(mapping, index, 1, false);
 
-		spin_lock_irq(&mapping->tree_lock);
+		xa_lock_irq(&mapping->i_pages);
 
-		slot = radix_tree_lookup_slot(&mapping->page_tree, index);
+		slot = radix_tree_lookup_slot(&mapping->i_pages, index);
 		VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
-					&mapping->tree_lock), page);
+					&mapping->i_pages.xa_lock), page);
 		VM_BUG_ON_PAGE(page_mapped(page), page);
 
 		/*
@@ -1431,14 +1431,14 @@ static void collapse_shmem(struct mm_struct *mm,
 		list_add_tail(&page->lru, &pagelist);
 
 		/* Finally, replace with the new page. */
-		radix_tree_replace_slot(&mapping->page_tree, slot,
+		radix_tree_replace_slot(&mapping->i_pages, slot,
 				new_page + (index % HPAGE_PMD_NR));
 
 		slot = radix_tree_iter_resume(slot, &iter);
 		index++;
 		continue;
 out_lru:
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		putback_lru_page(page);
 out_isolate_failed:
 		unlock_page(page);
@@ -1464,14 +1464,14 @@ out_unlock:
 		}
 
 		for (; index < end; index++) {
-			radix_tree_insert(&mapping->page_tree, index,
+			radix_tree_insert(&mapping->i_pages, index,
 					new_page + (index % HPAGE_PMD_NR));
 		}
 		nr_none += n;
 	}
 
 tree_locked:
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 tree_unlocked:
 
 	if (result == SCAN_SUCCEED) {
@@ -1520,9 +1520,8 @@ tree_unlocked:
 	} else {
 		/* Something went wrong: rollback changes to the radix-tree */
 		shmem_uncharge(mapping->host, nr_none);
-		spin_lock_irq(&mapping->tree_lock);
-		radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
-				start) {
+		xa_lock_irq(&mapping->i_pages);
+		radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
 			if (iter.index >= end)
 				break;
 			page = list_first_entry_or_null(&pagelist,
@@ -1532,8 +1531,7 @@ tree_unlocked:
 					break;
 				nr_none--;
 				/* Put holes back where they were */
-				radix_tree_delete(&mapping->page_tree,
-						  iter.index);
+				radix_tree_delete(&mapping->i_pages, iter.index);
 				continue;
 			}
 
@@ -1542,16 +1540,15 @@ tree_unlocked:
 			/* Unfreeze the page. */
 			list_del(&page->lru);
 			page_ref_unfreeze(page, 2);
-			radix_tree_replace_slot(&mapping->page_tree,
-						slot, page);
+			radix_tree_replace_slot(&mapping->i_pages, slot, page);
 			slot = radix_tree_iter_resume(slot, &iter);
-			spin_unlock_irq(&mapping->tree_lock);
+			xa_unlock_irq(&mapping->i_pages);
 			putback_lru_page(page);
 			unlock_page(page);
-			spin_lock_irq(&mapping->tree_lock);
+			xa_lock_irq(&mapping->i_pages);
 		}
 		VM_BUG_ON(nr_none);
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 
 		/* Unfreeze new_page, caller would take care about freeing it */
 		page_ref_unfreeze(new_page, 1);
@@ -1579,7 +1576,7 @@ static void khugepaged_scan_shmem(struct mm_struct *mm,
 	swap = 0;
 	memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
 	rcu_read_lock();
-	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
+	radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
 		if (iter.index >= start + HPAGE_PMD_NR)
 			break;
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7978c6faae06..e074f7c637aa 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5974,9 +5974,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 
 	/*
 	 * Interrupts should be disabled here because the caller holds the
-	 * mapping->tree_lock lock which is taken with interrupts-off. It is
+	 * i_pages lock which is taken with interrupts-off. It is
 	 * important here to have the interrupts disabled because it is the
-	 * only synchronisation we have for udpating the per-CPU variables.
+	 * only synchronisation we have for updating the per-CPU variables.
 	 */
 	VM_BUG_ON(!irqs_disabled());
 	mem_cgroup_charge_statistics(memcg, page, PageTransHuge(page),
diff --git a/mm/migrate.c b/mm/migrate.c
index 51b55f2d2db5..f65dd69e1fd1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -467,20 +467,21 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	oldzone = page_zone(page);
 	newzone = page_zone(newpage);
 
-	spin_lock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_pages);
 
-	pslot = radix_tree_lookup_slot(&mapping->page_tree,
+	pslot = radix_tree_lookup_slot(&mapping->i_pages,
  					page_index(page));
 
 	expected_count += 1 + page_has_private(page);
 	if (page_count(page) != expected_count ||
-		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
-		spin_unlock_irq(&mapping->tree_lock);
+		radix_tree_deref_slot_protected(pslot,
+					&mapping->i_pages.xa_lock) != page) {
+		xa_unlock_irq(&mapping->i_pages);
 		return -EAGAIN;
 	}
 
 	if (!page_ref_freeze(page, expected_count)) {
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		return -EAGAIN;
 	}
 
@@ -494,7 +495,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	if (mode == MIGRATE_ASYNC && head &&
 			!buffer_migrate_lock_buffers(head, mode)) {
 		page_ref_unfreeze(page, expected_count);
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		return -EAGAIN;
 	}
 
@@ -522,7 +523,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 		SetPageDirty(newpage);
 	}
 
-	radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
+	radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
 
 	/*
 	 * Drop cache reference from old page by unfreezing
@@ -531,7 +532,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	page_ref_unfreeze(page, expected_count - 1);
 
-	spin_unlock(&mapping->tree_lock);
+	xa_unlock(&mapping->i_pages);
 	/* Leave irq disabled to prevent preemption while updating stats */
 
 	/*
@@ -574,20 +575,19 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 	int expected_count;
 	void **pslot;
 
-	spin_lock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_pages);
 
-	pslot = radix_tree_lookup_slot(&mapping->page_tree,
-					page_index(page));
+	pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page));
 
 	expected_count = 2 + page_has_private(page);
 	if (page_count(page) != expected_count ||
-		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
-		spin_unlock_irq(&mapping->tree_lock);
+		radix_tree_deref_slot_protected(pslot, &mapping->i_pages.xa_lock) != page) {
+		xa_unlock_irq(&mapping->i_pages);
 		return -EAGAIN;
 	}
 
 	if (!page_ref_freeze(page, expected_count)) {
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		return -EAGAIN;
 	}
 
@@ -596,11 +596,11 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 
 	get_page(newpage);
 
-	radix_tree_replace_slot(&mapping->page_tree, pslot, newpage);
+	radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
 
 	page_ref_unfreeze(page, expected_count - 1);
 
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 
 	return MIGRATEPAGE_SUCCESS;
 }
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 586f31261c83..5c1a3279e63f 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2099,7 +2099,8 @@ void __init page_writeback_init(void)
  * so that it can tag pages faster than a dirtying process can create them).
  */
 /*
- * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce tree_lock latency.
+ * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce the i_pages lock
+ * latency.
  */
 void tag_pages_for_writeback(struct address_space *mapping,
 			     pgoff_t start, pgoff_t end)
@@ -2109,22 +2110,22 @@ void tag_pages_for_writeback(struct address_space *mapping,
 	struct radix_tree_iter iter;
 	void **slot;
 
-	spin_lock_irq(&mapping->tree_lock);
-	radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter, start,
+	xa_lock_irq(&mapping->i_pages);
+	radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start,
 							PAGECACHE_TAG_DIRTY) {
 		if (iter.index > end)
 			break;
-		radix_tree_iter_tag_set(&mapping->page_tree, &iter,
+		radix_tree_iter_tag_set(&mapping->i_pages, &iter,
 							PAGECACHE_TAG_TOWRITE);
 		tagged++;
 		if ((tagged % WRITEBACK_TAG_BATCH) != 0)
 			continue;
 		slot = radix_tree_iter_resume(slot, &iter);
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		cond_resched();
-		spin_lock_irq(&mapping->tree_lock);
+		xa_lock_irq(&mapping->i_pages);
 	}
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 }
 EXPORT_SYMBOL(tag_pages_for_writeback);
 
@@ -2467,13 +2468,13 @@ int __set_page_dirty_nobuffers(struct page *page)
 			return 1;
 		}
 
-		spin_lock_irqsave(&mapping->tree_lock, flags);
+		xa_lock_irqsave(&mapping->i_pages, flags);
 		BUG_ON(page_mapping(page) != mapping);
 		WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
 		account_page_dirtied(page, mapping);
-		radix_tree_tag_set(&mapping->page_tree, page_index(page),
+		radix_tree_tag_set(&mapping->i_pages, page_index(page),
 				   PAGECACHE_TAG_DIRTY);
-		spin_unlock_irqrestore(&mapping->tree_lock, flags);
+		xa_unlock_irqrestore(&mapping->i_pages, flags);
 		unlock_page_memcg(page);
 
 		if (mapping->host) {
@@ -2718,11 +2719,10 @@ int test_clear_page_writeback(struct page *page)
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
 		unsigned long flags;
 
-		spin_lock_irqsave(&mapping->tree_lock, flags);
+		xa_lock_irqsave(&mapping->i_pages, flags);
 		ret = TestClearPageWriteback(page);
 		if (ret) {
-			radix_tree_tag_clear(&mapping->page_tree,
-						page_index(page),
+			radix_tree_tag_clear(&mapping->i_pages, page_index(page),
 						PAGECACHE_TAG_WRITEBACK);
 			if (bdi_cap_account_writeback(bdi)) {
 				struct bdi_writeback *wb = inode_to_wb(inode);
@@ -2736,7 +2736,7 @@ int test_clear_page_writeback(struct page *page)
 						     PAGECACHE_TAG_WRITEBACK))
 			sb_clear_inode_writeback(mapping->host);
 
-		spin_unlock_irqrestore(&mapping->tree_lock, flags);
+		xa_unlock_irqrestore(&mapping->i_pages, flags);
 	} else {
 		ret = TestClearPageWriteback(page);
 	}
@@ -2766,7 +2766,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
 		unsigned long flags;
 
-		spin_lock_irqsave(&mapping->tree_lock, flags);
+		xa_lock_irqsave(&mapping->i_pages, flags);
 		ret = TestSetPageWriteback(page);
 		if (!ret) {
 			bool on_wblist;
@@ -2774,8 +2774,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 			on_wblist = mapping_tagged(mapping,
 						   PAGECACHE_TAG_WRITEBACK);
 
-			radix_tree_tag_set(&mapping->page_tree,
-						page_index(page),
+			radix_tree_tag_set(&mapping->i_pages, page_index(page),
 						PAGECACHE_TAG_WRITEBACK);
 			if (bdi_cap_account_writeback(bdi))
 				inc_wb_stat(inode_to_wb(inode), WB_WRITEBACK);
@@ -2789,14 +2788,12 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 				sb_mark_inode_writeback(mapping->host);
 		}
 		if (!PageDirty(page))
-			radix_tree_tag_clear(&mapping->page_tree,
-						page_index(page),
+			radix_tree_tag_clear(&mapping->i_pages, page_index(page),
 						PAGECACHE_TAG_DIRTY);
 		if (!keep_write)
-			radix_tree_tag_clear(&mapping->page_tree,
-						page_index(page),
+			radix_tree_tag_clear(&mapping->i_pages, page_index(page),
 						PAGECACHE_TAG_TOWRITE);
-		spin_unlock_irqrestore(&mapping->tree_lock, flags);
+		xa_unlock_irqrestore(&mapping->i_pages, flags);
 	} else {
 		ret = TestSetPageWriteback(page);
 	}
@@ -2816,7 +2813,7 @@ EXPORT_SYMBOL(__test_set_page_writeback);
  */
 int mapping_tagged(struct address_space *mapping, int tag)
 {
-	return radix_tree_tagged(&mapping->page_tree, tag);
+	return radix_tree_tagged(&mapping->i_pages, tag);
 }
 EXPORT_SYMBOL(mapping_tagged);
 
diff --git a/mm/readahead.c b/mm/readahead.c
index 4d57b4644f98..539bbb6c1fad 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -175,7 +175,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
 			break;
 
 		rcu_read_lock();
-		page = radix_tree_lookup(&mapping->page_tree, page_offset);
+		page = radix_tree_lookup(&mapping->i_pages, page_offset);
 		rcu_read_unlock();
 		if (page && !radix_tree_exceptional_entry(page))
 			continue;
diff --git a/mm/rmap.c b/mm/rmap.c
index 9122787c4947..f0dd4e4565bc 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -32,11 +32,11 @@
  *                 mmlist_lock (in mmput, drain_mmlist and others)
  *                 mapping->private_lock (in __set_page_dirty_buffers)
  *                   mem_cgroup_{begin,end}_page_stat (memcg->move_lock)
- *                     mapping->tree_lock (widely used)
+ *                     i_pages lock (widely used)
  *                 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)
- *                   mapping->tree_lock (widely used, in set_page_dirty,
+ *                   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)
  *
diff --git a/mm/shmem.c b/mm/shmem.c
index 4424fc0c33aa..9d6c7e595415 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -332,12 +332,12 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
 
 	VM_BUG_ON(!expected);
 	VM_BUG_ON(!replacement);
-	item = __radix_tree_lookup(&mapping->page_tree, index, &node, &pslot);
+	item = __radix_tree_lookup(&mapping->i_pages, index, &node, &pslot);
 	if (!item)
 		return -ENOENT;
 	if (item != expected)
 		return -ENOENT;
-	__radix_tree_replace(&mapping->page_tree, node, pslot,
+	__radix_tree_replace(&mapping->i_pages, node, pslot,
 			     replacement, NULL);
 	return 0;
 }
@@ -355,7 +355,7 @@ static bool shmem_confirm_swap(struct address_space *mapping,
 	void *item;
 
 	rcu_read_lock();
-	item = radix_tree_lookup(&mapping->page_tree, index);
+	item = radix_tree_lookup(&mapping->i_pages, index);
 	rcu_read_unlock();
 	return item == swp_to_radix_entry(swap);
 }
@@ -590,14 +590,14 @@ static int shmem_add_to_page_cache(struct page *page,
 	page->mapping = mapping;
 	page->index = index;
 
-	spin_lock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_pages);
 	if (PageTransHuge(page)) {
 		void __rcu **results;
 		pgoff_t idx;
 		int i;
 
 		error = 0;
-		if (radix_tree_gang_lookup_slot(&mapping->page_tree,
+		if (radix_tree_gang_lookup_slot(&mapping->i_pages,
 					&results, &idx, index, 1) &&
 				idx < index + HPAGE_PMD_NR) {
 			error = -EEXIST;
@@ -605,14 +605,14 @@ static int shmem_add_to_page_cache(struct page *page,
 
 		if (!error) {
 			for (i = 0; i < HPAGE_PMD_NR; i++) {
-				error = radix_tree_insert(&mapping->page_tree,
+				error = radix_tree_insert(&mapping->i_pages,
 						index + i, page + i);
 				VM_BUG_ON(error);
 			}
 			count_vm_event(THP_FILE_ALLOC);
 		}
 	} else if (!expected) {
-		error = radix_tree_insert(&mapping->page_tree, index, page);
+		error = radix_tree_insert(&mapping->i_pages, index, page);
 	} else {
 		error = shmem_radix_tree_replace(mapping, index, expected,
 								 page);
@@ -624,10 +624,10 @@ static int shmem_add_to_page_cache(struct page *page,
 			__inc_node_page_state(page, NR_SHMEM_THPS);
 		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
 		__mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 	} else {
 		page->mapping = NULL;
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		page_ref_sub(page, nr);
 	}
 	return error;
@@ -643,13 +643,13 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 
 	VM_BUG_ON_PAGE(PageCompound(page), page);
 
-	spin_lock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_pages);
 	error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
 	page->mapping = NULL;
 	mapping->nrpages--;
 	__dec_node_page_state(page, NR_FILE_PAGES);
 	__dec_node_page_state(page, NR_SHMEM);
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_unlock_irq(&mapping->i_pages);
 	put_page(page);
 	BUG_ON(error);
 }
@@ -662,9 +662,9 @@ static int shmem_free_swap(struct address_space *mapping,
 {
 	void *old;
 
-	spin_lock_irq(&mapping->tree_lock);
-	old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
-	spin_unlock_irq(&mapping->tree_lock);
+	xa_lock_irq(&mapping->i_