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>

fs/hugetlbfs/inode.c

@@ -374,7 +374,7 @@ static void truncate_hugepages(struct inode *inode, loff_t lstart)
 static void hugetlbfs_evict_inode(struct inode *inode)
 {
 	truncate_hugepages(inode, 0);
-	clear_inode(inode);
+	end_writeback(inode);
 }
 
 static inline void

fs/inode.c

@@ -294,6 +294,18 @@ void __iget(struct inode *inode)
 	inodes_stat.nr_unused--;
 }
 
+void end_writeback(struct inode *inode)
+{
+	might_sleep();
+	BUG_ON(inode->i_data.nrpages);
+	BUG_ON(!list_empty(&inode->i_data.private_list));
+	BUG_ON(!(inode->i_state & I_FREEING));
+	BUG_ON(inode->i_state & I_CLEAR);
+	inode_sync_wait(inode);
+	inode->i_state = I_FREEING | I_CLEAR;
+}
+EXPORT_SYMBOL(end_writeback);
+
 /**
  * clear_inode - clear an inode
  * @inode: inode to clear

include/linux/fs.h

@@ -2184,6 +2184,7 @@ extern void unlock_new_inode(struct inode *);
 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 *);