[PATCH] Introduce sys_splice() system call

This adds support for the sys_splice system call. Using a pipe as a
transport, it can connect to files or sockets (latter as output only).

From the splice.c comments:

   "splice": joining two ropes together by interweaving their strands.

   This is the "extended pipe" functionality, where a pipe is used as
   an arbitrary in-memory buffer. Think of a pipe as a small kernel
   buffer that you can use to transfer data from one end to the other.

   The traditional unix read/write is extended with a "splice()" operation
   that transfers data buffers to or from a pipe buffer.

   Named by Larry McVoy, original implementation from Linus, extended by
   Jens to support splicing to files and fixing the initial implementation
   bugs.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

6 files changed, 15 insertions, 4 deletions

diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h
index 014e3562895b..789e9bdd0a40 100644
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -318,8 +318,9 @@
 #define __NR_unshare            310
 #define __NR_set_robust_list    311
 #define __NR_get_robust_list    312
+#define __NR_sys_splice         313
 
-#define NR_syscalls 313
+#define NR_syscalls 314
 
 /*
  * user-visible error numbers are in the range -1 - -128: see
diff --git a/include/asm-ia64/unistd.h b/include/asm-ia64/unistd.h
index 019956c613e4..36070c1014d8 100644
--- a/include/asm-ia64/unistd.h
+++ b/include/asm-ia64/unistd.h
@@ -285,12 +285,13 @@
 #define __NR_faccessat                  1293
 /* 1294, 1295 reserved for pselect/ppoll */
 #define __NR_unshare                    1296
+#define __NR_splice                     1297
 
 #ifdef __KERNEL__
 
 #include <linux/config.h>
 
-#define NR_syscalls                     273 /* length of syscall table */
+#define NR_syscalls                     274 /* length of syscall table */
 
 #define __ARCH_WANT_SYS_RT_SIGACTION
 
diff --git a/include/asm-powerpc/unistd.h b/include/asm-powerpc/unistd.h
index 1e990747dce7..536ba0873052 100644
--- a/include/asm-powerpc/unistd.h
+++ b/include/asm-powerpc/unistd.h
@@ -301,8 +301,9 @@
 #define __NR_pselect6           280
 #define __NR_ppoll              281
 #define __NR_unshare            282
+#define __NR_splice             283
 
-#define __NR_syscalls           283
+#define __NR_syscalls           284
 
 #ifdef __KERNEL__
 #define __NR__exit __NR_exit
diff --git a/include/asm-x86_64/unistd.h b/include/asm-x86_64/unistd.h
index fcc516353087..f21ff2c1e960 100644
--- a/include/asm-x86_64/unistd.h
+++ b/include/asm-x86_64/unistd.h
@@ -609,8 +609,10 @@ __SYSCALL(__NR_unshare,	sys_unshare)
 __SYSCALL(__NR_set_robust_list, sys_set_robust_list)
 #define __NR_get_robust_list    274
 __SYSCALL(__NR_get_robust_list, sys_get_robust_list)
+#define __NR_splice             275
+__SYSCALL(__NR_splice, sys_splice)
 
-#define __NR_syscall_max __NR_get_robust_list
+#define __NR_syscall_max __NR_splice
 
 #ifndef __NO_STUBS
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 408fe89498f4..20fa5f6d7269 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1032,6 +1032,8 @@ struct file_operations {
         int (*check_flags)(int);
         int (*dir_notify)(struct file *filp, unsigned long arg);
         int (*flock) (struct file *, int, struct file_lock *);
+        ssize_t (*splice_write)(struct inode *, struct file *, size_t, unsigned int);
+        ssize_t (*splice_read)(struct file *, struct inode *, size_t, unsigned int);
 };
 
 struct inode_operations {
@@ -1609,6 +1611,8 @@ extern ssize_t generic_file_sendfile(struct file *, loff_t *, size_t, read_actor
 extern void do_generic_mapping_read(struct address_space *mapping,
                                     struct file_ra_state *, struct file *,
                                     loff_t *, read_descriptor_t *, read_actor_t);
+extern ssize_t generic_file_splice_read(struct file *, struct inode *, size_t, unsigned int);
+extern ssize_t generic_file_splice_write(struct inode *, struct file *, size_t, unsigned int);
 extern void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
 extern ssize_t generic_file_readv(struct file *filp, const struct iovec *iov, 
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e487e3b60f60..e78ffc7d5b56 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -569,5 +569,7 @@ 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);
 
 #endif