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

On Mon, Aug 04, 2008 at 03:52:37PM +0200, Thomas Petazzoni wrote:
Le Sat, 2 Aug 2008 12:38:48 -0400,
"J. Bruce Fields" <bfields@xxxxxxxxxxxx> a écrit :

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

Then also need disabling.

OK by me, but again, why exactly? Since you're replacing the locking
calls they used by stubs that just return errors, in theory nfs, nfsd,
gfs2, and the rest should still compile and run, just without locking
support, right?

I don't have a strong opinion either way, just curious.

--b.

Updated patch below.

Thanks!

Thomas

---

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@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 | 15 ++++++++++++++-
fs/Makefile | 3 ++-
fs/dlm/Kconfig | 1 +
fs/gfs2/Kconfig | 1 +
fs/proc/proc_misc.c | 4 ++++
include/linux/fs.h | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
kernel/sys_ni.c | 1 +
kernel/sysctl.c | 6 +++++-
8 files changed, 73 insertions(+), 10 deletions(-)

Index: linuxdev/fs/Kconfig
===================================================================
--- linuxdev.orig/fs/Kconfig
+++ linuxdev/fs/Kconfig
@@ -427,12 +427,21 @@
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"

config OCFS2_FS
tristate "OCFS2 file system support"
depends on NET && SYSFS
+ depends on FILE_LOCKING
select CONFIGFS_FS
select JBD
select CRC32
@@ -642,6 +651,7 @@

config FUSE_FS
tristate "Filesystem in Userspace support"
+ depends on FILE_LOCKING
help
With FUSE it is possible to implement a fully functional filesystem
in a userspace program.
@@ -1567,7 +1577,7 @@

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
@@ -1735,6 +1745,7 @@

config LOCKD
tristate
+ depends on FILE_LOCKING

config LOCKD_V4
bool
@@ -1870,6 +1881,7 @@
config CIFS
tristate "CIFS support (advanced network filesystem, SMBFS successor)"
depends on INET
+ depends on FILE_LOCKING
select NLS
help
This is the client VFS module for the Common Internet File System
@@ -2059,6 +2071,7 @@
config AFS_FS
tristate "Andrew File System support (AFS) (EXPERIMENTAL)"
depends on INET && EXPERIMENTAL
+ depends on FILE_LOCKING
select AF_RXRPC
help
If you say Y here, you will get an experimental Andrew File System
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/dlm/Kconfig
===================================================================
--- linuxdev.orig/fs/dlm/Kconfig
+++ linuxdev/fs/dlm/Kconfig
@@ -2,6 +2,7 @@
tristate "Distributed Lock Manager (DLM)"
depends on EXPERIMENTAL && INET
depends on SYSFS && (IPV6 || IPV6=n)
+ depends on FILE_LOCKING
select CONFIGFS_FS
select IP_SCTP
help
Index: linuxdev/fs/gfs2/Kconfig
===================================================================
--- linuxdev.orig/fs/gfs2/Kconfig
+++ linuxdev/fs/gfs2/Kconfig
@@ -1,6 +1,7 @@
config GFS2_FS
tristate "GFS2 file system support"
depends on EXPERIMENTAL && (64BIT || (LSF && LBD))
+ depends on FILE_LOCKING
select FS_POSIX_ACL
select CRC32
help
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/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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