From 1bf9d14dff4a2c4de6152c6f751bdaf6896b68bb Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 16 Jun 2013 20:27:42 +0400
Subject: [PATCH] new helper: fixed_size_llseek()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/read_write.c    | 20 ++++++++++++++++++++
 include/linux/fs.h |  2 ++
 2 files changed, 22 insertions(+)

diff --git a/fs/read_write.c b/fs/read_write.c
index f646c8b565b9..782dfc3acebc 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -144,6 +144,26 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int whence)
 }
 EXPORT_SYMBOL(generic_file_llseek);
 
+/**
+ * fixed_size_llseek - llseek implementation for fixed-sized devices
+ * @file:	file structure to seek on
+ * @offset:	file offset to seek to
+ * @whence:	type of seek
+ * @size:	size of the file
+ *
+ */
+loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t size)
+{
+	switch (whence) {
+	case SEEK_SET: case SEEK_CUR: case SEEK_END:
+		return generic_file_llseek_size(file, offset, whence,
+						size, size);
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(fixed_size_llseek);
+
 /**
  * noop_llseek - No Operation Performed llseek implementation
  * @file:	file structure to seek on
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1db01c13ddce..803b7fa2520a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2428,6 +2428,8 @@ extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
 		int whence, loff_t maxsize, loff_t eof);
+extern loff_t fixed_size_llseek(struct file *file, loff_t offset,
+		int whence, loff_t size);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);