new helper: end_writeback()

Essentially, the minimal variant of ->evict_inode().  It's
a trimmed-down clear_inode(), sans any fs callbacks.  Once
it returns we know that no async writeback will be happening;
every ->evict_inode() instance should do that once and do that
before doing anything ->write_inode() could interfere with
(e.g. freeing the on-disk inode).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e0ecb8e..3c23c1d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2184,6 +2184,7 @@
 extern void __iget(struct inode * inode);
 extern void iget_failed(struct inode *);
 extern void clear_inode(struct inode *);
+extern void end_writeback(struct inode *);
 extern void destroy_inode(struct inode *);
 extern void __destroy_inode(struct inode *);
 extern struct inode *new_inode(struct super_block *);