ext4: switch to ->iterate_shared()

Note that we need relax_dir() equivalent for directories
locked shared.

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

fs/ext4/dir.c

@@ -266,7 +266,7 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
 			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 						sb->s_blocksize);
 		}
-		if ((ctx->pos < inode->i_size) && !dir_relax(inode))
+		if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
 			goto done;
 		brelse(bh);
 		bh = NULL;
@@ -644,7 +644,7 @@ int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
 const struct file_operations ext4_dir_operations = {
 	.llseek		= ext4_dir_llseek,
 	.read		= generic_read_dir,
-	.iterate	= ext4_readdir,
+	.iterate_shared	= ext4_readdir,
 	.unlocked_ioctl = ext4_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= ext4_compat_ioctl,

include/linux/fs.h

@@ -3134,6 +3134,13 @@ static inline bool dir_relax(struct inode *inode)
 	return !IS_DEADDIR(inode);
 }
 
+static inline bool dir_relax_shared(struct inode *inode)
+{
+	inode_unlock_shared(inode);
+	inode_lock_shared(inode);
+	return !IS_DEADDIR(inode);
+}
+
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);