Re: [PATCH 6/6] fs/splice: full support for compiling out splice

[Josh Triplett <josh@joshtriplett.org>]

On Sat, Nov 22, 2014 at 10:00:01PM +0100, Pieter Smith wrote:
> Entirely compile out splice translation unit when the system is configured
> without splice family of syscalls (i.e. CONFIG_SYSCALL_SPLICE is undefined).
> 
> add/remove: 0/25 grow/shrink: 0/5 up/down: 0/-4845 (-4845)

Very nice!

- Josh Triplett

> function                                     old     new   delta
> pipe_to_null                                   4       -      -4
> generic_pipe_buf_nosteal                       6       -      -6
> spd_release_page                              10       -     -10
> PageUptodate                                  22      11     -11
> lock_page                                     36      24     -12
> page_cache_pipe_buf_release                   16       -     -16
> splice_write_null                             24       4     -20
> page_cache_pipe_buf_ops                       20       -     -20
> nosteal_pipe_buf_ops                          20       -     -20
> default_pipe_buf_ops                          20       -     -20
> generic_splice_sendpage                       24       -     -24
> splice_shrink_spd                             27       -     -27
> direct_splice_actor                           47       -     -47
> default_file_splice_write                     49       -     -49
> wakeup_pipe_writers                           54       -     -54
> write_pipe_buf                                71       -     -71
> page_cache_pipe_buf_confirm                   80       -     -80
> splice_grow_spd                               87       -     -87
> splice_from_pipe                              93       -     -93
> splice_from_pipe_next                        106       -    -106
> pipe_to_sendpage                             109       -    -109
> page_cache_pipe_buf_steal                    114       -    -114
> generic_file_splice_read                     131       8    -123
> do_splice_direct                             148       -    -148
> __splice_from_pipe                           246       -    -246
> splice_direct_to_actor                       416       -    -416
> splice_to_pipe                               417       -    -417
> default_file_splice_read                     688       -    -688
> iter_file_splice_write                       702       4    -698
> __generic_file_splice_read                  1109       -   -1109
> 
> Signed-off-by: Pieter Smith <pieter@boesman.nl>
> ---
>  fs/Makefile            |  3 ++-
>  fs/splice.c            |  2 --
>  include/linux/fs.h     | 26 ++++++++++++++++++++++++++
>  include/linux/splice.h | 43 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 71 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/Makefile b/fs/Makefile
> index fb7646e..9395622 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -10,7 +10,7 @@ obj-y :=	open.o read_write.o file_table.o super.o \
>  		ioctl.o readdir.o select.o dcache.o inode.o \
>  		attr.o bad_inode.o file.o filesystems.o namespace.o \
>  		seq_file.o xattr.o libfs.o fs-writeback.o \
> -		pnode.o splice.o sync.o utimes.o \
> +		pnode.o sync.o utimes.o \
>  		stack.o fs_struct.o statfs.o fs_pin.o
>  
>  ifeq ($(CONFIG_BLOCK),y)
> @@ -22,6 +22,7 @@ endif
>  obj-$(CONFIG_PROC_FS) += proc_namespace.o
>  
>  obj-$(CONFIG_FSNOTIFY)		+= notify/
> +obj-$(CONFIG_SYSCALL_SPLICE)	+= splice.o
>  obj-$(CONFIG_EPOLL)		+= eventpoll.o
>  obj-$(CONFIG_ANON_INODES)	+= anon_inodes.o
>  obj-$(CONFIG_SIGNALFD)		+= signalfd.o
> diff --git a/fs/splice.c b/fs/splice.c
> index 7c4c695..44b201b 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1316,7 +1316,6 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
>  	return ret;
>  }
>  
> -#ifdef CONFIG_SYSCALL_SPLICE
>  static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
>  			       struct pipe_inode_info *opipe,
>  			       size_t len, unsigned int flags);
> @@ -2201,5 +2200,4 @@ COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
>  	return do_sendfile(out_fd, in_fd, NULL, count, 0);
>  }
>  #endif
> -#endif
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 04c0975..9b3054e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2449,6 +2449,7 @@ extern void block_sync_page(struct page *page);
>  #define __splice_p(x) NULL
>  #endif
>  
> +#ifdef CONFIG_SYSCALL_SPLICE
>  /* fs/splice.c */
>  extern ssize_t generic_file_splice_read(struct file *, loff_t *,
>  		struct pipe_inode_info *, size_t, unsigned int);
> @@ -2458,6 +2459,31 @@ extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
>  		struct file *, loff_t *, size_t, unsigned int);
>  extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
>  		struct file *out, loff_t *, size_t len, unsigned int flags);
> +#else
> +static inline ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
> +		struct pipe_inode_info *pipe, size_t len, unsigned int flags)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
> +		struct pipe_inode_info *pipe, size_t len, unsigned int flags)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t iter_file_splice_write(struct pipe_inode_info *pipe,
> +		struct file *out, loff_t *ppos, size_t len, unsigned int flags)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
> +		struct file *out, loff_t *ppos, size_t len, unsigned int flags)
> +{
> +	return -EPERM;
> +}
> +#endif
>  
>  extern void
>  file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
> diff --git a/include/linux/splice.h b/include/linux/splice.h
> index da2751d..50ca77f 100644
> --- a/include/linux/splice.h
> +++ b/include/linux/splice.h
> @@ -65,6 +65,7 @@ typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
>  typedef int (splice_direct_actor)(struct pipe_inode_info *,
>  				  struct splice_desc *);
>  
> +#ifdef CONFIG_SYSCALL_SPLICE
>  extern ssize_t splice_from_pipe(struct pipe_inode_info *, struct file *,
>  				loff_t *, size_t, unsigned int,
>  				splice_actor *);
> @@ -74,13 +75,55 @@ extern ssize_t splice_to_pipe(struct pipe_inode_info *,
>  			      struct splice_pipe_desc *);
>  extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
>  				      splice_direct_actor *);
> +#else /* #ifdef CONFIG_SYSCALL_SPLICE */
> +static inline ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
> +			 loff_t *ppos, size_t len, unsigned int flags,
> +			 splice_actor *actor)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
> +			   splice_actor *actor)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
> +		       struct splice_pipe_desc *spd)
> +{
> +	return -EPERM;
> +}
> +
> +static inline ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
> +			       splice_direct_actor *actor)
> +{
> +	return -EPERM;
> +}
> +#endif /* #ifdef CONFIG_SYSCALL_SPLICE */
>  
>  /*
>   * for dynamic pipe sizing
>   */
> +#ifdef CONFIG_SYSCALL_SPLICE
>  extern int splice_grow_spd(const struct pipe_inode_info *, struct splice_pipe_desc *);
>  extern void splice_shrink_spd(struct splice_pipe_desc *);
>  extern void spd_release_page(struct splice_pipe_desc *, unsigned int);
> +#else /* #ifdef CONFIG_SYSCALL_SPLICE */
> +static inline int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
> +{
> +	return -EPERM;
> +}
> +
> +static inline void splice_shrink_spd(struct splice_pipe_desc *spd)
> +{
> +}
> +
> +static inline void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
> +{
> +}
> +#endif /* #ifdef CONFIG_SYSCALL_SPLICE */
>  
>  extern const struct pipe_buf_operations page_cache_pipe_buf_ops;
> +
>  #endif
> -- 
> 1.9.1
>