[PATCH 2/2] fs: Support compiling out sendfile

From: Pieter Smith
Date: Mon Oct 20 2014 - 17:49:51 EST


Many embedded systems will not need this syscall, and omitting it
saves space. Add a new EXPERT config option CONFIG_SENDFILE_SYSCALL
(default y) to support compiling it out.

bloat-o-meter:
add/remove: 0/4 grow/shrink: 5/0 up/down: 23/-751 (-728)
function old new delta
sys_pwritev 115 122 +7
sys_preadv 115 122 +7
fdput_pos 29 36 +7
sys_pwrite64 115 116 +1
sys_pread64 115 116 +1
fdput 11 - -11
sys_sendfile 122 - -122
sys_sendfile64 126 - -126
do_sendfile 492 - -492

Signed-off-by: Pieter Smith <pieter@xxxxxxxxxx>
---
fs/Makefile | 3 ++-
init/Kconfig | 10 ++++++++++
kernel/sys_ni.c | 4 ++++
3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/fs/Makefile b/fs/Makefile
index 1e3423f..1bbfea7 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -5,7 +5,7 @@
# Rewritten to use lists instead of if-statements.
#

-obj-y := open.o read_write.o sendfile.o file_table.o super.o \
+obj-y := open.o read_write.o file_table.o super.o \
char_dev.o stat.o exec.o pipe.o namei.o fcntl.o \
ioctl.o readdir.o select.o dcache.o inode.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
@@ -38,6 +38,7 @@ obj-$(CONFIG_COMPAT_BINFMT_ELF) += compat_binfmt_elf.o
obj-$(CONFIG_BINFMT_ELF_FDPIC) += binfmt_elf_fdpic.o
obj-$(CONFIG_BINFMT_SOM) += binfmt_som.o
obj-$(CONFIG_BINFMT_FLAT) += binfmt_flat.o
+obj-$(CONFIG_SENDFILE_SYSCALL) += sendfile.o

obj-$(CONFIG_FS_MBCACHE) += mbcache.o
obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o
diff --git a/init/Kconfig b/init/Kconfig
index 782a65b..df6785c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1547,6 +1547,16 @@ config ADVISE_SYSCALLS
applications use these syscalls, you can disable this option to save
space.

+config SENDFILE_SYSCALL
+ bool "Enable sendfile syscall" if EXPERT
+ default y
+ help
+ This option enables the sendfile syscall, used by applications to copy
+ data between file descriptors. Because sendfile performs the copying
+ within the kernel, it is more efficient than the combination of read
+ and write. If building an embedded system where no applications use
+ the sendfile syscall, 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 d4709d4..b068de7 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -159,6 +159,10 @@ cond_syscall(sys_uselib);
cond_syscall(sys_fadvise64);
cond_syscall(sys_fadvise64_64);
cond_syscall(sys_madvise);
+cond_syscall(sys_sendfile);
+cond_syscall(sys_sendfile64);
+cond_syscall(compat_sys_sendfile);
+cond_syscall(compat_sys_sendfile64);

/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);
--
1.9.1

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