Configure out file locking features

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:

   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@selenic.com>, and is part of the Linux Tiny project.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: matthew@wil.cx
Cc: linux-fsdevel@vger.kernel.org
Cc: mpm@selenic.com
Cc: akpm@linux-foundation.org
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

3 files changed, 14 insertions, 1 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index abccb5dab9a8..c6ae4d4842eb 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -419,6 +419,14 @@ config FS_POSIX_ACL
         bool
         default n
 
+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.
+
 source "fs/xfs/Kconfig"
 source "fs/gfs2/Kconfig"
 
diff --git a/fs/Makefile b/fs/Makefile
index a1482a5eff15..4b86d433baaf 100644
--- a/fs/Makefile
+++ b/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 aio.o \
                 seq_file.o xattr.o libfs.o fs-writeback.o \
                 pnode.o drop_caches.o splice.o sync.o utimes.o \
@@ -27,6 +27,7 @@ obj-$(CONFIG_ANON_INODES)	+= anon_inodes.o
 obj-$(CONFIG_SIGNALFD)          += signalfd.o
 obj-$(CONFIG_TIMERFD)           += timerfd.o
 obj-$(CONFIG_EVENTFD)           += eventfd.o
+obj-$(CONFIG_FILE_LOCKING)      += locks.o
 obj-$(CONFIG_COMPAT)            += compat.o compat_ioctl.o
 
 nfsd-$(CONFIG_NFSD)             := nfsctl.o
diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 29e20c6b1f7f..1aabbe2592e1 100644
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -684,6 +684,7 @@ static int cmdline_read_proc(char *page, char **start, off_t off,
         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);
@@ -695,6 +696,7 @@ static const struct file_operations proc_locks_operations = {
         .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)
@@ -888,7 +890,9 @@ void __init proc_misc_init(void)
 #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