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>

1 files changed, 20 insertions, 23 deletions

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);