orangefs: Provide a splice-read wrapper

Provide a splice_read wrapper for ocfs2. This increments the read stats
and then locks the inode across the call to filemap_splice_read() and a
revalidation of the mapping. Splicing from direct I/O is done by the
caller.

Signed-off-by: David Howells <[e-mail]>
cc: Christoph Hellwig <[e-mail]>
cc: Al Viro <[e-mail]>
cc: Jens Axboe <[e-mail]>
cc: Mike Marshall <[e-mail]>
cc: Martin Brandenburg <[e-mail]>
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

fs/orangefs/file.c

···
 	return ret;
 }
 
+static ssize_t orangefs_file_splice_read(struct file *in, loff_t *ppos,
+					 struct pipe_inode_info *pipe,
+					 size_t len, unsigned int flags)
+{
+	struct inode *inode = file_inode(in);
+	ssize_t ret;
+
+	orangefs_stats.reads++;
+
+	down_read(&inode->i_rwsem);
+	ret = orangefs_revalidate_mapping(inode);
+	if (ret)
+		goto out;
+
+	ret = filemap_splice_read(in, ppos, pipe, len, flags);
+out:
+	up_read(&inode->i_rwsem);
+	return ret;
+}
+
 static ssize_t orangefs_file_write_iter(struct kiocb *iocb,
     struct iov_iter *iter)
 {
···
 	.lock		= orangefs_lock,
 	.mmap		= orangefs_file_mmap,
 	.open		= generic_file_open,
-	.splice_read    = generic_file_splice_read,
+	.splice_read    = orangefs_file_splice_read,
 	.splice_write   = iter_file_splice_write,
 	.flush		= orangefs_flush,
 	.release	= orangefs_file_release,