[PATCH] splice: add direct fd <-> fd splicing support

It's more efficient for sendfile() emulation. Basically we cache an
internal private pipe and just use that as the intermediate area for
pages. Direct splicing is not available from sys_splice(), it is only
meant to be used for sendfile() emulation.

Additional patch from Ingo Molnar to avoid the PIPE_BUFFERS loop at
exit for the normal fast path.

Signed-off-by: Jens Axboe <axboe@suse.de>

3 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7e6454454fbd..9e8e2ee353b4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1613,6 +1613,8 @@ extern void do_generic_mapping_read(struct address_space *mapping,
                                     loff_t *, read_descriptor_t *, read_actor_t);
 extern ssize_t generic_file_splice_read(struct file *, struct pipe_inode_info *, size_t, unsigned int);
 extern ssize_t generic_file_splice_write(struct pipe_inode_info *, struct file *, size_t, unsigned int);
+extern long do_splice_direct(struct file *in, struct file *out,
+                             size_t len, unsigned int flags);
 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/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 9cf99cb34c15..660e9d866e5d 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -58,6 +58,7 @@ void pipe_wait(struct pipe_inode_info *pipe);
 
 struct pipe_inode_info * alloc_pipe_info(struct inode * inode);
 void free_pipe_info(struct inode * inode);
+void __free_pipe_info(struct pipe_inode_info *);
 
 /*
  * splice is tied to pipes as a transport (at least for now), so we'll just
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 541f4828f5e7..e194ec75833d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -684,6 +684,7 @@ static inline void prefetch_stack(struct task_struct *t) { }
 
 struct audit_context;           /* See audit.c */
 struct mempolicy;
+struct pipe_inode_info;
 
 enum sleep_type {
         SLEEP_NORMAL,
@@ -882,6 +883,11 @@ struct task_struct {
 
         atomic_t fs_excl;       /* holding fs exclusive resources */
         struct rcu_head rcu;
+
+        /*
+         * cache last used pipe for splice
+         */
+        struct pipe_inode_info *splice_pipe;
 };
 
 static inline pid_t process_group(struct task_struct *tsk)