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

Josh Triplett
2014-11-22T21:53:27Z

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
>