On Tue, Nov 25, 2014 at 12:01:02AM +0100, Pieter Smith wrote: > Many embedded systems will not need the splice-family syscalls (splice, > vmsplice, tee and sendfile). Omitting them saves space. This adds a new EXPERT > config option CONFIG_SYSCALL_SPLICE (default y) to support compiling them out. > > The goal is to completely compile out fs/splice along with the syscalls. To > achieve this, the remaining patch-set will deal with fs/splice exports. As far > as possible, the impact on other device drivers will be minimized so as to > reduce the overal maintenance burden of CONFIG_SYSCALL_SPLICE. > > The use of exported functions will be solved by transparently mocking them out > with static inlines. Uses of the exported pipe_buf_operations struct however > require direct modification in fs/fuse and net/core. The next two patches will > deal with this. A macro is defined that will assist with NULL'ing out callbacks > when CONFIG_SYSCALL_SPLICE is undefined: __splice_p(). This message needs updating, since the patch series doesn't introduce or use __splice_p anymore. > Once all exports are solved, fs/splice can be compiled out. > > The bloat benefit of this patch given a tinyconfig is: > > add/remove: 0/16 grow/shrink: 2/5 up/down: 114/-3693 (-3579) > function old new delta > splice_direct_to_actor 348 416 +68 > splice_to_pipe 371 417 +46 > splice_from_pipe_next 107 106 -1 > fdput 11 - -11 > signal_pending 39 26 -13 > fdget 56 42 -14 > user_page_pipe_buf_ops 20 - -20 > user_page_pipe_buf_steal 25 - -25 > file_end_write 58 29 -29 > file_start_write 68 34 -34 > pipe_to_user 43 - -43 > wakeup_pipe_readers 54 - -54 > do_splice_to 87 - -87 > ipipe_prep.part 92 - -92 > opipe_prep.part 119 - -119 > sys_sendfile 122 - -122 > sys_sendfile64 126 - -126 > sys_vmsplice 137 - -137 > vmsplice_to_user 205 - -205 > sys_tee 491 - -491 > do_sendfile 492 - -492 > vmsplice_to_pipe 558 - -558 > sys_splice 1020 - -1020 > > Signed-off-by: Pieter Smith <pieter@xxxxxxxxxx> > --- > fs/splice.c | 2 ++ > init/Kconfig | 10 ++++++++++ > kernel/sys_ni.c | 8 ++++++++ > 3 files changed, 20 insertions(+) > > diff --git a/fs/splice.c b/fs/splice.c > index 44b201b..7c4c695 100644 > --- a/fs/splice.c > +++ b/fs/splice.c > @@ -1316,6 +1316,7 @@ 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); > @@ -2200,4 +2201,5 @@ 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/init/Kconfig b/init/Kconfig > index d811d5f..dec9819 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1571,6 +1571,16 @@ config NTP > system clock to an NTP server, you can disable this option to save > space. > > +config SYSCALL_SPLICE > + bool "Enable splice/vmsplice/tee/sendfile syscalls" if EXPERT > + default y > + help > + This option enables the splice, vmsplice, tee and sendfile syscalls. These > + are used by applications to: move data between buffers and arbitrary file > + descriptors; "copy" data between buffers; or copy data from userspace into > + buffers. If building an embedded system where no applications use these > + syscalls, you can disable this option to save space. > + > config PCI_QUIRKS > default y > bool "Enable PCI quirk workarounds" if EXPERT > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index d2f5b00..25d5551 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -170,6 +170,14 @@ cond_syscall(sys_fstat); > cond_syscall(sys_stat); > cond_syscall(sys_uname); > cond_syscall(sys_olduname); > +cond_syscall(sys_vmsplice); > +cond_syscall(sys_splice); > +cond_syscall(sys_tee); > +cond_syscall(sys_sendfile); > +cond_syscall(sys_sendfile64); > +cond_syscall(compat_sys_vmsplice); > +cond_syscall(compat_sys_sendfile); > +cond_syscall(compat_sys_sendfile64); > > /* arch-specific weak syscall entries */ > cond_syscall(sys_pciconfig_read); > -- > 2.1.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
