VFS: implement sendfile file operation

Currently the sendfile syscalls hardcode assumptions about the
implementation of the read file operations implementation.  Although
it checks for the presence of a readpage address-space operation
filesystems in Linux are free to implement read differently from
the generic version (generic_file_read).  Many filesystems such
as tmpfs, smbfs or xfs chose to implement it differently and need
additional locking, revalidation or checks. 

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 21aa43cc5c4d..1d3334ca66d9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -757,6 +757,7 @@ struct file_operations {
 	int (*lock) (struct file *, int, struct file_lock *);
 	ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, loff_t *);
 	ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, loff_t *);
+	ssize_t (*sendfile) (struct file *, struct file *, loff_t *, size_t);
 	ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
 	unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
 };
@@ -1234,6 +1235,7 @@ extern int generic_file_mmap(struct file *, struct vm_area_struct *);
 extern int file_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size);
 extern ssize_t generic_file_read(struct file *, char *, size_t, loff_t *);
 extern ssize_t generic_file_write(struct file *, const char *, size_t, loff_t *);
+extern ssize_t generic_file_sendfile(struct file *, struct file *, loff_t *, size_t);
 extern void do_generic_file_read(struct file *, loff_t *, read_descriptor_t *, read_actor_t);
 ssize_t generic_file_direct_IO(int rw, struct inode *inode, char *buf,
 				loff_t offset, size_t count);