Re: [patch 2/4] Configure out file locking features

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On Thu, Jul 31, 2008 at 11:27:05AM +0200, Thomas Petazzoni wrote:
> This patch adds the CONFIG_FILE_LOCKING option which allows to remove
> support for advisory locks. With this patch enabled, the flock()
> system call, the F_GETLK, F_SETLK and F_SETLKW operations of fcntl()
> and NFS support are disabled. These features are not necessarly needed
> on embedded systems. It allows to save ~11 Kb of kernel code and data:

Out of curiosity, why does the nfs client need disabling, but not nfsd,
gfs2, fuse, etc.?

--b.

> 
>    text	   data	    bss	    dec	    hex	filename
> 1125436	 118764	 212992	1457192	 163c28	vmlinux.old
> 1114299	 118564	 212992	1445855	 160fdf	vmlinux
>  -11137    -200       0  -11337   -2C49 +/-
> 
> This patch has originally been written by Matt Mackall
> <mpm@xxxxxxxxxxx>, and is part of the Linux Tiny project.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Matt Mackall <mpm@xxxxxxxxxxx>
> Cc: matthew@xxxxxx
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: mpm@xxxxxxxxxxx
> Cc: akpm@xxxxxxxxxxxxxxxxxxxx
> 
> ---
>  fs/Kconfig          |    2 +-
>  fs/Makefile         |    3 ++-
>  fs/proc/proc_misc.c |    4 ++++
>  include/linux/fs.h  |   52 +++++++++++++++++++++++++++++++++++++++++++++-------
>  init/Kconfig        |    8 ++++++++
>  kernel/sys_ni.c     |    1 +
>  kernel/sysctl.c     |    6 +++++-
>  7 files changed, 66 insertions(+), 10 deletions(-)
> 
> Index: linuxdev/fs/Kconfig
> ===================================================================
> --- linuxdev.orig/fs/Kconfig
> +++ linuxdev/fs/Kconfig
> @@ -1559,7 +1559,7 @@
>  
>  config NFS_FS
>  	tristate "NFS client support"
> -	depends on INET
> +	depends on INET && FILE_LOCKING
>  	select LOCKD
>  	select SUNRPC
>  	select NFS_ACL_SUPPORT if NFS_V3_ACL
> Index: linuxdev/fs/Makefile
> ===================================================================
> --- linuxdev.orig/fs/Makefile
> +++ linuxdev/fs/Makefile
> @@ -7,7 +7,7 @@
>  
>  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 locks.o dcache.o inode.o \
> +		ioctl.o readdir.o select.o fifo.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 drop_caches.o splice.o sync.o utimes.o \
> @@ -28,6 +28,7 @@
>  obj-$(CONFIG_TIMERFD)		+= timerfd.o
>  obj-$(CONFIG_EVENTFD)		+= eventfd.o
>  obj-$(CONFIG_AIO)               += aio.o
> +obj-$(CONFIG_FILE_LOCKING)      += locks.o
>  obj-$(CONFIG_COMPAT)		+= compat.o compat_ioctl.o
>  
>  nfsd-$(CONFIG_NFSD)		:= nfsctl.o
> Index: linuxdev/fs/proc/proc_misc.c
> ===================================================================
> --- linuxdev.orig/fs/proc/proc_misc.c
> +++ linuxdev/fs/proc/proc_misc.c
> @@ -677,6 +677,7 @@
>  	return proc_calc_metrics(page, start, off, count, eof, len);
>  }
>  
> +#ifdef CONFIG_FILE_LOCKING
>  static int locks_open(struct inode *inode, struct file *filp)
>  {
>  	return seq_open(filp, &locks_seq_operations);
> @@ -688,6 +689,7 @@
>  	.llseek		= seq_lseek,
>  	.release	= seq_release,
>  };
> +#endif /* CONFIG_FILE_LOCKING */
>  
>  static int execdomains_read_proc(char *page, char **start, off_t off,
>  				 int count, int *eof, void *data)
> @@ -881,7 +883,9 @@
>  #ifdef CONFIG_PRINTK
>  	proc_create("kmsg", S_IRUSR, NULL, &proc_kmsg_operations);
>  #endif
> +#ifdef CONFIG_FILE_LOCKING
>  	proc_create("locks", 0, NULL, &proc_locks_operations);
> +#endif
>  	proc_create("devices", 0, NULL, &proc_devinfo_operations);
>  	proc_create("cpuinfo", 0, NULL, &proc_cpuinfo_operations);
>  #ifdef CONFIG_BLOCK
> Index: linuxdev/include/linux/fs.h
> ===================================================================
> --- linuxdev.orig/include/linux/fs.h
> +++ linuxdev/include/linux/fs.h
> @@ -983,6 +983,13 @@
>  
>  #include <linux/fcntl.h>
>  
> +extern void send_sigio(struct fown_struct *fown, int fd, int band);
> +
> +/* fs/sync.c */
> +extern int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
> +			loff_t endbyte, unsigned int flags);
> +
> +#ifdef CONFIG_FILE_LOCKING
>  extern int fcntl_getlk(struct file *, struct flock __user *);
>  extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
>  			struct flock __user *);
> @@ -993,14 +1000,9 @@
>  			struct flock64 __user *);
>  #endif
>  
> -extern void send_sigio(struct fown_struct *fown, int fd, int band);
>  extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
>  extern int fcntl_getlease(struct file *filp);
>  
> -/* fs/sync.c */
> -extern int do_sync_mapping_range(struct address_space *mapping, loff_t offset,
> -			loff_t endbyte, unsigned int flags);
> -
>  /* fs/locks.c */
>  extern void locks_init_lock(struct file_lock *);
>  extern void locks_copy_lock(struct file_lock *, struct file_lock *);
> @@ -1023,6 +1025,33 @@
>  extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
>  extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
>  extern struct seq_operations locks_seq_operations;
> +#else /* !CONFIG_FILE_LOCKING */
> +#define fcntl_getlk(a, b) (-EINVAL)
> +#define fcntl_setlk(a, b, c, d) (-EACCES)
> +#if BITS_PER_LONG == 32
> +#define fcntl_getlk64(a, b) (-EINVAL)
> +#define fcntl_setlk64(a, b, c, d) (-EACCES)
> +#endif
> +#define fcntl_setlease(a, b, c) (0)
> +#define fcntl_getlease(a) (0)
> +#define locks_init_lock(a)
> +#define locks_copy_lock(a, b)
> +#define locks_remove_posix(a, b)
> +#define locks_remove_flock(a)
> +#define posix_test_lock(a, b) (0)
> +#define posix_lock_file(a, b) (-ENOLCK)
> +#define posix_lock_file_wait(a, b) (-ENOLCK)
> +#define posix_unblock_lock(a, b) (-ENOENT)
> +#define vfs_test_lock(a, b) (0)
> +#define vfs_lock_file(a, b, c, d) (-ENOLCK)
> +#define vfs_cancel_lock(a, b) (0)
> +#define flock_lock_file_wait(a, b) (-ENOLCK)
> +#define __break_lease(a, b) (0)
> +#define lease_get_mtime(a, b)
> +#define lock_may_read(a, b, c) (1)
> +#define lock_may_write(a, b, c) (1)
> +#endif /* !CONFIG_FILE_LOCKING */
> +
>  
>  struct fasync_struct {
>  	int	magic;
> @@ -1554,9 +1583,12 @@
>  /* /sys/fs */
>  extern struct kobject *fs_kobj;
>  
> +extern int rw_verify_area(int, struct file *, loff_t *, size_t);
> +
>  #define FLOCK_VERIFY_READ  1
>  #define FLOCK_VERIFY_WRITE 2
>  
> +#ifdef CONFIG_FILE_LOCKING
>  extern int locks_mandatory_locked(struct inode *);
>  extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);
>  
> @@ -1587,8 +1619,6 @@
>  	return 0;
>  }
>  
> -extern int rw_verify_area(int, struct file *, loff_t *, size_t);
> -
>  static inline int locks_verify_truncate(struct inode *inode,
>  				    struct file *filp,
>  				    loff_t size)
> @@ -1609,6 +1639,14 @@
>  		return __break_lease(inode, mode);
>  	return 0;
>  }
> +#else /* !CONFIG_FILE_LOCKING */
> +#define locks_mandatory_locked(a) (0)
> +#define locks_mandatory_area(a, b, c, d, e) (0)
> +#define mandatory_lock(a) (0)
> +#define locks_verify_locked(a) (0)
> +#define locks_verify_truncate(a, b, c) (0)
> +#define break_lease(a, b) (0)
> +#endif /* CONFIG_FILE_LOCKING */
>  
>  /* fs/open.c */
>  
> Index: linuxdev/init/Kconfig
> ===================================================================
> --- linuxdev.orig/init/Kconfig
> +++ linuxdev/init/Kconfig
> @@ -732,6 +732,14 @@
>            by some high performance threaded applications. Disabling
>            this option saves about 7k.
>  
> +config FILE_LOCKING
> +	bool "Enable POSIX file locking API" if EMBEDDED
> +	default y
> +	help
> +	  This option enables standard file locking support, required
> +          for filesystems like NFS and for the flock() system
> +          call. Disabling this option saves about 11k.
> +
>  config VM_EVENT_COUNTERS
>  	default y
>  	bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
> Index: linuxdev/kernel/sys_ni.c
> ===================================================================
> --- linuxdev.orig/kernel/sys_ni.c
> +++ linuxdev/kernel/sys_ni.c
> @@ -130,6 +130,7 @@
>  cond_syscall(sys_io_submit);
>  cond_syscall(sys_io_cancel);
>  cond_syscall(sys_io_getevents);
> +cond_syscall(sys_flock);
>  
>  /* arch-specific weak syscall entries */
>  cond_syscall(sys_pciconfig_read);
> Index: linuxdev/kernel/sysctl.c
> ===================================================================
> --- linuxdev.orig/kernel/sysctl.c
> +++ linuxdev/kernel/sysctl.c
> @@ -97,7 +97,7 @@
>  static int neg_one = -1;
>  #endif
>  
> -#ifdef CONFIG_MMU
> +#if defined(CONFIG_MMU) && defined(CONFIG_FILE_LOCKING)
>  static int two = 2;
>  #endif
>  
> @@ -1260,6 +1260,7 @@
>  		.extra1		= &minolduid,
>  		.extra2		= &maxolduid,
>  	},
> +#ifdef CONFIG_FILE_LOCKING
>  	{
>  		.ctl_name	= FS_LEASES,
>  		.procname	= "leases-enable",
> @@ -1268,6 +1269,7 @@
>  		.mode		= 0644,
>  		.proc_handler	= &proc_dointvec,
>  	},
> +#endif
>  #ifdef CONFIG_DNOTIFY
>  	{
>  		.ctl_name	= FS_DIR_NOTIFY,
> @@ -1279,6 +1281,7 @@
>  	},
>  #endif
>  #ifdef CONFIG_MMU
> +#ifdef CONFIG_FILE_LOCKING
>  	{
>  		.ctl_name	= FS_LEASE_TIME,
>  		.procname	= "lease-break-time",
> @@ -1290,6 +1293,7 @@
>  		.extra1		= &zero,
>  		.extra2		= &two,
>  	},
> +#endif /* CONFIG_FILE_LOCKING */
>  #ifdef CONFIG_AIO
>  	{
>  		.procname	= "aio-nr",
> 
> -- 
> Thomas Petazzoni, Free Electrons
> Kernel, drivers and embedded Linux development,
> consulting, training and support.
> http://free-electrons.com
> --
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