vfs: add generic_file_llseek_size

Add a generic_file_llseek variant to the VFS that allows passing in
the maximum file size of the file system, instead of always
using maxbytes from the superblock.

This can be used to eliminate some cut'n'paste seek code in ext4.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index db85196..d055cc7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2403,6 +2403,8 @@
 extern loff_t noop_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
+extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
+		int origin, loff_t maxsize);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);