[patch] make dnotify compile-time configurable

From: Robert Love
Date: Fri Oct 01 2004 - 01:26:15 EST

Attached patch makes dnotify compile-time configurable via
CONFIG_DNOTIFY. The patch stands alone from the inotify patch, although
it really makes most sense in that context. Maybe the tiny kernel will
find it useful as well.

On a desktop system with inotify, there is no reason to enable dnotify
support. The primary user of dnotify (FAM) already supports inotify
(via Gamin). Many non-desktop systems do not use dnotify.

There was a sysctl, dir_notify_enable, for run-time configuration of
dnotify. I removed it. It makes no sense to me, even without
compile-time configuration, to disable this feature. With the ability
to compile dnotify away, a sysctl makes even less sense (which, as it
made zero sense before, makes no sense in and of itself now).

Disabling CONFIG_DNOTIFY saves a couple hundred bytes off of vmlinux.

When disabled, fcntl(fd, F_NOTIFY, ...) returns -EINVAL.

Best,

Robert Love

make dnotify compile-time configurable via CONFIG_DNOTIFY because, well,
dnotify sucks

Signed-Off-By: Robert Love <rml@xxxxxxxxxx>

Documentation/dnotify.txt | 8 ++++++++
fs/Kconfig | 12 ++++++++++++
fs/Makefile | 13 +++++++------
fs/dnotify.c | 8 +-------
include/linux/dnotify.h | 46 +++++++++++++++++++++++++++++++++++++++++-----
include/linux/fs.h | 2 +-
kernel/sysctl.c | 8 --------
7 files changed, 70 insertions(+), 27 deletions(-)

diff -urN linux-2.6.9-rc2/Documentation/dnotify.txt linux/Documentation/dnotify.txt
--- linux-2.6.9-rc2/Documentation/dnotify.txt 2004-08-14 06:55:33.000000000 -0400
+++ linux/Documentation/dnotify.txt 2004-10-01 02:20:50.615450192 -0400
@@ -54,6 +54,14 @@
Also, files that are unlinked, will still cause notifications in the
last directory that they were linked to.

+Configuration
+-------------
+
+Dnotify is controlled via the CONFIG_DNOTIFY configuration option. When
+disabled, fcntl(fd, F_NOTIFY, ...) will return -EINVAL.
+
+Dnotify is deprecated in favor of inotify (CONFIG_INOTIFY).
+
Example
-------

diff -urN linux-2.6.9-rc2/fs/dnotify.c linux/fs/dnotify.c
--- linux-2.6.9-rc2/fs/dnotify.c 2004-08-14 06:55:10.000000000 -0400
+++ linux/fs/dnotify.c 2004-10-01 02:04:01.264894800 -0400
@@ -13,6 +13,7 @@
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
+
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/sched.h>
@@ -21,8 +22,6 @@
#include <linux/spinlock.h>
#include <linux/slab.h>

-int dir_notify_enable = 1;
-
static kmem_cache_t *dn_cache;

static void redo_inode_mask(struct inode *inode)
@@ -72,8 +71,6 @@
dnotify_flush(filp, id);
return 0;
}
- if (!dir_notify_enable)
- return -EINVAL;
inode = filp->f_dentry->d_inode;
if (!S_ISDIR(inode->i_mode))
return -ENOTDIR;
@@ -157,9 +154,6 @@
{
struct dentry *parent;

- if (!dir_notify_enable)
- return;
-
spin_lock(&dentry->d_lock);
parent = dentry->d_parent;
if (parent->d_inode->i_dnotify_mask & event) {
diff -urN linux-2.6.9-rc2/fs/Kconfig linux/fs/Kconfig
--- linux-2.6.9-rc2/fs/Kconfig 2004-09-21 00:55:17.000000000 -0400
+++ linux/fs/Kconfig 2004-10-01 02:01:02.218114048 -0400
@@ -438,6 +438,18 @@
depends on XFS_QUOTA || QUOTA
default y

+config DNOTIFY
+ bool "Dnotify support"
+ default y
+ help
+ Dnotify is a directory-based per-fd file change notification system
+ that uses signals to communicate events to user-space. It has
+ been replaced by inotify (see CONFIG_INOTIFY), which solves many of
+ the shortcomings of dnotify and adds new features, but some
+ applications may still rely on dnotify.
+
+ Because of this, if unsure, say Y.
+
config AUTOFS_FS
tristate "Kernel automounter support"
help
diff -urN linux-2.6.9-rc2/fs/Makefile linux/fs/Makefile
--- linux-2.6.9-rc2/fs/Makefile 2004-09-21 00:55:17.000000000 -0400
+++ linux/fs/Makefile 2004-10-01 02:00:57.627811880 -0400
@@ -5,12 +5,11 @@
# Rewritten to use lists instead of if-statements.
#

-obj-y := open.o read_write.o file_table.o buffer.o \
- bio.o super.o block_dev.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 attr.o bad_inode.o file.o dnotify.o \
- filesystems.o namespace.o seq_file.o xattr.o libfs.o \
- fs-writeback.o mpage.o direct-io.o aio.o
+obj-y := open.o read_write.o file_table.o buffer.o bio.o super.o \
+ block_dev.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 \
+ attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \
+ seq_file.o xattr.o libfs.o fs-writeback.o mpage.o direct-io.o \

obj-$(CONFIG_EPOLL) += eventpoll.o
obj-$(CONFIG_COMPAT) += compat.o
@@ -37,6 +36,8 @@
obj-$(CONFIG_QFMT_V2) += quota_v2.o
obj-$(CONFIG_QUOTACTL) += quota.o

+obj-$(CONFIG_DNOTIFY) += dnotify.o
+
obj-$(CONFIG_PROC_FS) += proc/
obj-y += partitions/
obj-$(CONFIG_SYSFS) += sysfs/
diff -urN linux-2.6.9-rc2/include/linux/dnotify.h linux/include/linux/dnotify.h
--- linux-2.6.9-rc2/include/linux/dnotify.h 2004-08-14 06:54:47.000000000 -0400
+++ linux/include/linux/dnotify.h 2004-10-01 01:56:48.868629024 -0400
@@ -1,3 +1,5 @@
+#ifndef _LINUX_DNOTIFY_H
+#define _LINUX_DNOTIFY_H
/*
* Directory notification for Linux
*
@@ -8,20 +10,54 @@

struct dnotify_struct {
struct dnotify_struct * dn_next;
- unsigned long dn_mask; /* Events to be notified
- see linux/fcntl.h */
+ unsigned long dn_mask;
int dn_fd;
struct file * dn_filp;
fl_owner_t dn_owner;
};

+#ifdef __KERNEL__
+
+#include <linux/config.h>
+
+#ifdef CONFIG_DNOTIFY
+
extern void __inode_dir_notify(struct inode *, unsigned long);
-extern void dnotify_flush(struct file *filp, fl_owner_t id);
+extern void dnotify_flush(struct file *, fl_owner_t);
extern int fcntl_dirnotify(int, struct file *, unsigned long);
-void dnotify_parent(struct dentry *dentry, unsigned long event);
+extern void dnotify_parent(struct dentry *, unsigned long);

static inline void inode_dir_notify(struct inode *inode, unsigned long event)
{
- if ((inode)->i_dnotify_mask & (event))
+ if (inode->i_dnotify_mask & (event))
__inode_dir_notify(inode, event);
}
+
+#else
+
+static inline void __inode_dir_notify(struct inode *inode, unsigned long event)
+{
+}
+
+static inline void dnotify_flush(struct file *filp, fl_owner_t id)
+{
+}
+
+static inline int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
+{
+ return -EINVAL;
+}
+
+static inline void dnotify_parent(struct dentry *dentry, unsigned long event)
+{
+}
+
+static inline void inode_dir_notify(struct inode *inode, unsigned long event)
+{
+}
+
+#endif /* CONFIG_DNOTIFY */
+
+#endif /* __KERNEL __ */
+
+#endif /* _LINUX_DNOTIFY_H */
diff -urN linux-2.6.9-rc2/include/linux/fs.h linux/include/linux/fs.h
--- linux-2.6.9-rc2/include/linux/fs.h 2004-09-21 00:55:18.000000000 -0400
+++ linux/include/linux/fs.h 2004-10-01 02:04:15.245769384 -0400
@@ -61,7 +61,7 @@
};
extern struct inodes_stat_t inodes_stat;

-extern int leases_enable, dir_notify_enable, lease_break_time;
+extern int leases_enable, lease_break_time;

#define NR_FILE 8192 /* this can well be larger on a larger system */
#define NR_RESERVED_FILES 10 /* reserved for root */
diff -urN linux-2.6.9-rc2/kernel/sysctl.c linux/kernel/sysctl.c
--- linux-2.6.9-rc2/kernel/sysctl.c 2004-09-21 00:55:18.000000000 -0400
+++ linux/kernel/sysctl.c 2004-10-01 02:03:44.610426664 -0400
@@ -879,14 +879,6 @@
.proc_handler = &proc_dointvec,
},
{
- .ctl_name = FS_DIR_NOTIFY,
- .procname = "dir-notify-enable",
- .data = &dir_notify_enable,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = &proc_dointvec,
- },
- {
.ctl_name = FS_LEASE_TIME,
.procname = "lease-break-time",
.data = &lease_break_time,