From: Thomas Petazzoni This patchs adds the CONFIG_AIO option which allows to remove support for asynchronous I/O operations, that are not necessarly used by applications, particularly on embedded devices. As this is a size-reduction option, it depends on CONFIG_EMBEDDED. It allows to save ~7 kilobytes of kernel code/data: text data bss dec hex filename 1115067 119180 217088 1451335 162547 vmlinux 1108025 119048 217088 1444161 160941 vmlinux.new -7042 -132 0 -7174 -1C06 +/- This patch has been originally written by Matt Mackall , and is part of the Linux Tiny project. Signed-off-by: Thomas Petazzoni Cc: Benjamin LaHaise Cc: Zach Brown Signed-off-by: Matt Mackall Signed-off-by: Andrew Morton --- fs/Makefile | 3 ++- include/linux/aio.h | 9 +++++++++ init/Kconfig | 8 ++++++++ kernel/sys_ni.c | 5 +++++ kernel/sysctl.c | 2 ++ 5 files changed, 26 insertions(+), 1 deletion(-) diff -puN fs/Makefile~configure-out-aio-support fs/Makefile --- a/fs/Makefile~configure-out-aio-support +++ a/fs/Makefile @@ -8,7 +8,7 @@ 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 fifo.o dcache.o inode.o \ - attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \ + attr.o bad_inode.o file.o filesystems.o namespace.o \ seq_file.o xattr.o libfs.o fs-writeback.o \ pnode.o drop_caches.o splice.o sync.o utimes.o \ stack.o @@ -27,6 +27,7 @@ obj-$(CONFIG_ANON_INODES) += anon_inodes obj-$(CONFIG_SIGNALFD) += signalfd.o obj-$(CONFIG_TIMERFD) += timerfd.o obj-$(CONFIG_EVENTFD) += eventfd.o +obj-$(CONFIG_AIO) += aio.o obj-$(CONFIG_FILE_LOCKING) += locks.o obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o diff -puN include/linux/aio.h~configure-out-aio-support include/linux/aio.h --- a/include/linux/aio.h~configure-out-aio-support +++ a/include/linux/aio.h @@ -204,12 +204,21 @@ struct kioctx { /* prototypes */ extern unsigned aio_max_size; +#ifdef CONFIG_AIO extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb); extern int aio_put_req(struct kiocb *iocb); extern void kick_iocb(struct kiocb *iocb); extern int aio_complete(struct kiocb *iocb, long res, long res2); struct mm_struct; extern void exit_aio(struct mm_struct *mm); +#else +static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; } +static inline int aio_put_req(struct kiocb *iocb) { return 0; } +static inline void kick_iocb(struct kiocb *iocb) { } +static inline int aio_complete(struct kiocb *iocb, long res, long res2) { return 0; } +struct mm_struct; +static inline void exit_aio(struct mm_struct *mm) { } +#endif /* CONFIG_AIO */ #define io_wait_to_kiocb(wait) container_of(wait, struct kiocb, ki_wait) diff -puN init/Kconfig~configure-out-aio-support init/Kconfig --- a/init/Kconfig~configure-out-aio-support +++ a/init/Kconfig @@ -758,6 +758,14 @@ config IGMP Disabling this option removes support for the Internet group management protocol, used for multicast. Saves about 10k. +config AIO + bool "Enable AIO support" if EMBEDDED + default y + help + This option enables POSIX asynchronous I/O which may by used + by some high performance threaded applications. Disabling + this option saves about 7k. + config VM_EVENT_COUNTERS default y bool "Enable VM event counters for /proc/vmstat" if EMBEDDED diff -puN kernel/sys_ni.c~configure-out-aio-support kernel/sys_ni.c --- a/kernel/sys_ni.c~configure-out-aio-support +++ a/kernel/sys_ni.c @@ -126,6 +126,11 @@ cond_syscall(sys_vm86); cond_syscall(compat_sys_ipc); cond_syscall(compat_sys_sysctl); cond_syscall(sys_flock); +cond_syscall(sys_io_setup); +cond_syscall(sys_io_destroy); +cond_syscall(sys_io_submit); +cond_syscall(sys_io_cancel); +cond_syscall(sys_io_getevents); /* arch-specific weak syscall entries */ cond_syscall(sys_pciconfig_read); diff -puN kernel/sysctl.c~configure-out-aio-support kernel/sysctl.c --- a/kernel/sysctl.c~configure-out-aio-support +++ a/kernel/sysctl.c @@ -1343,6 +1343,7 @@ static struct ctl_table fs_table[] = { .mode = 0444, .proc_handler = &proc_doulongvec_minmax, }, +#ifdef CONFIG_AIO { .procname = "aio-max-nr", .data = &aio_max_nr, @@ -1350,6 +1351,7 @@ static struct ctl_table fs_table[] = { .mode = 0644, .proc_handler = &proc_doulongvec_minmax, }, +#endif /* CONFIG_AIO */ #ifdef CONFIG_INOTIFY_USER { .ctl_name = FS_INOTIFY, _