convert btrfs to ->evict_inode()

NB: do we want btrfs_wait_ordered_range() on eviction of
inodes with positive i_nlink on subvolume with zero root_refs?
If not, btrfs_evict_inode() can be simplified by unconditionally
bailing out in case of i_nlink > 0 in the very beginning...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/btrfs/ctree.h

@@ -2389,7 +2389,7 @@ unsigned long btrfs_force_ra(struct address_space *mapping,
 			      pgoff_t offset, pgoff_t last_index);
 int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf);
 int btrfs_readpage(struct file *file, struct page *page);
-void btrfs_delete_inode(struct inode *inode);
+void btrfs_evict_inode(struct inode *inode);
 void btrfs_put_inode(struct inode *inode);
 int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc);
 void btrfs_dirty_inode(struct inode *inode);

fs/btrfs/inode.c

@@ -3668,18 +3668,22 @@ static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
 	return err;
 }
 
-void btrfs_delete_inode(struct inode *inode)
+void btrfs_evict_inode(struct inode *inode)
 {
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	unsigned long nr;
 	int ret;
 
 	truncate_inode_pages(&inode->i_data, 0);
+	if (inode->i_nlink && btrfs_root_refs(&root->root_item) != 0)
+		goto no_delete;
+
 	if (is_bad_inode(inode)) {
 		btrfs_orphan_del(NULL, inode);
 		goto no_delete;
 	}
+	/* do we really want it for ->i_nlink > 0 and zero btrfs_root_refs? */
 	btrfs_wait_ordered_range(inode, 0, (u64)-1);
 
 	if (root->fs_info->log_root_recovering) {
@@ -3729,7 +3733,7 @@ void btrfs_delete_inode(struct inode *inode)
 	btrfs_end_transaction(trans, root);
 	btrfs_btree_balance_dirty(root, nr);
 no_delete:
-	clear_inode(inode);
+	end_writeback(inode);
 	return;
 }
 

fs/btrfs/super.c

@@ -797,7 +797,7 @@ static int btrfs_unfreeze(struct super_block *sb)
 
 static const struct super_operations btrfs_super_ops = {
 	.drop_inode	= btrfs_drop_inode,
-	.delete_inode	= btrfs_delete_inode,
+	.evict_inode	= btrfs_evict_inode,
 	.put_super	= btrfs_put_super,
 	.sync_fs	= btrfs_sync_fs,
 	.show_options	= btrfs_show_options,