[PATCH] splice: add optional input and output offsets

add optional input and output offsets to sys_splice(), for seekable file
descriptors:

 asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
                            int fd_out, loff_t __user *off_out,
                            size_t len, unsigned int flags);

semantics are straightforward: f_pos will be updated with the offset
provided by user-space, before the splice transfer is about to begin.
Providing a NULL offset pointer means the existing f_pos will be used
(and updated in situ).  Providing an offset for a pipe results in
-ESPIPE. Providing an invalid offset pointer results in -EFAULT.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 5717147..4c292fa 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -569,8 +569,11 @@ asmlinkage long compat_sys_newfstatat(unsigned int dfd, char __user * filename,
 asmlinkage long compat_sys_openat(unsigned int dfd, const char __user *filename,
 				   int flags, int mode);
 asmlinkage long sys_unshare(unsigned long unshare_flags);
-asmlinkage long sys_splice(int fdin, int fdout, size_t len,
-				unsigned int flags);
+
+asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
+			   int fd_out, loff_t __user *off_out,
+			   size_t len, unsigned int flags);
+
 asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 					int flags);