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>
diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index c21e0b4..dec98ca 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -193,9 +193,9 @@ int nilfs_btnode_prepare_change_key(struct address_space *btnc,
 				       (unsigned long long)oldkey,
 				       (unsigned long long)newkey);
 
-		spin_lock_irq(&btnc->tree_lock);
-		err = radix_tree_insert(&btnc->page_tree, newkey, obh->b_page);
-		spin_unlock_irq(&btnc->tree_lock);
+		xa_lock_irq(&btnc->i_pages);
+		err = radix_tree_insert(&btnc->i_pages, newkey, obh->b_page);
+		xa_unlock_irq(&btnc->i_pages);
 		/*
 		 * Note: page->index will not change to newkey until
 		 * nilfs_btnode_commit_change_key() will be called.
@@ -251,11 +251,11 @@ void nilfs_btnode_commit_change_key(struct address_space *btnc,
 				       (unsigned long long)newkey);
 		mark_buffer_dirty(obh);
 
-		spin_lock_irq(&btnc->tree_lock);
-		radix_tree_delete(&btnc->page_tree, oldkey);
-		radix_tree_tag_set(&btnc->page_tree, newkey,
+		xa_lock_irq(&btnc->i_pages);
+		radix_tree_delete(&btnc->i_pages, oldkey);
+		radix_tree_tag_set(&btnc->i_pages, newkey,
 				   PAGECACHE_TAG_DIRTY);
-		spin_unlock_irq(&btnc->tree_lock);
+		xa_unlock_irq(&btnc->i_pages);
 
 		opage->index = obh->b_blocknr = newkey;
 		unlock_page(opage);
@@ -283,9 +283,9 @@ void nilfs_btnode_abort_change_key(struct address_space *btnc,
 		return;
 
 	if (nbh == NULL) {	/* blocksize == pagesize */
-		spin_lock_irq(&btnc->tree_lock);
-		radix_tree_delete(&btnc->page_tree, newkey);
-		spin_unlock_irq(&btnc->tree_lock);
+		xa_lock_irq(&btnc->i_pages);
+		radix_tree_delete(&btnc->i_pages, newkey);
+		xa_unlock_irq(&btnc->i_pages);
 		unlock_page(ctxt->bh->b_page);
 	} else
 		brelse(nbh);