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SubjectRe: [patch] make dnotify a configure-time option
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On Mon, 2004-10-25 at 21:49 -0700, Andrew Morton wrote:

> It's actually a sysctl and is also present in 2.4. I doubt if it's very
> useful but it seems a bit random to be deleting it now.

Well, let's not pretend that we care about interfaces outside of
syscalls. Removing the sysctl simply results in a return of ENOTDIR
from sysctl(2). Nothing should break.

But, yah, it is a bit random. OK. How about keeping the sysctl, but
only when CONFIG_DNOTIFY=y?

Here is a version of the patch that leaves the sysctl in when dnotify is
enabled, and removes it otherwise. Is this better?

Thanks,

Robert Love


make dnotify configurable, via CONFIG_DNOTIFY.

Documentation/dnotify.txt | 6 ++++++
fs/Kconfig | 11 +++++++++++
fs/Makefile | 13 +++++++------
include/linux/dnotify.h | 46 +++++++++++++++++++++++++++++++++++++++++-----
include/linux/fs.h | 8 +++++++-
kernel/sysctl.c | 2 ++
6 files changed, 74 insertions(+), 12 deletions(-)

diff -urN linux-2.6.9-mm1/Documentation/dnotify.txt linux/Documentation/dnotify.txt
--- linux-2.6.9-mm1/Documentation/dnotify.txt 2004-10-18 17:54:32.000000000 -0400
+++ linux/Documentation/dnotify.txt 2004-10-26 01:03:44.120633208 -0400
@@ -54,6 +54,12 @@
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.
+
Example
-------

diff -urN linux-2.6.9-mm1/fs/Kconfig linux/fs/Kconfig
--- linux-2.6.9-mm1/fs/Kconfig 2004-10-26 00:14:31.924435248 -0400
+++ linux/fs/Kconfig 2004-10-26 01:03:44.122632904 -0400
@@ -440,6 +440,17 @@
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. There exist
+ superior alternatives, 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-mm1/fs/Makefile linux/fs/Makefile
--- linux-2.6.9-mm1/fs/Makefile 2004-10-26 00:14:31.933433880 -0400
+++ linux/fs/Makefile 2004-10-26 01:03:44.123632752 -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-mm1/include/linux/dnotify.h linux/include/linux/dnotify.h
--- linux-2.6.9-mm1/include/linux/dnotify.h 2004-10-18 17:53:06.000000000 -0400
+++ linux/include/linux/dnotify.h 2004-10-26 01:03:44.123632752 -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-mm1/include/linux/fs.h linux/include/linux/fs.h
--- linux-2.6.9-mm1/include/linux/fs.h 2004-10-26 00:14:32.890288416 -0400
+++ linux/include/linux/fs.h 2004-10-26 01:04:12.726284488 -0400
@@ -61,7 +61,11 @@
};
extern struct inodes_stat_t inodes_stat;

-extern int leases_enable, dir_notify_enable, lease_break_time;
+extern int leases_enable, lease_break_time;
+
+#ifdef CONFIG_DNOTIFY
+extern int dir_notify_enable;
+#endif

#define NR_FILE 8192 /* this can well be larger on a larger system */
#define NR_RESERVED_FILES 10 /* reserved for root */
@@ -464,8 +468,10 @@

__u32 i_generation;

+#ifdef CONFIG_DNOTIFY
unsigned long i_dnotify_mask; /* Directory notify events */
struct dnotify_struct *i_dnotify; /* for directory notifications */
+#endif

unsigned long i_state;
unsigned long dirtied_when; /* jiffies of first dirtying */
diff -urN linux-2.6.9-mm1/kernel/sysctl.c linux/kernel/sysctl.c
--- linux-2.6.9-mm1/kernel/sysctl.c 2004-10-26 00:14:33.274230048 -0400
+++ linux/kernel/sysctl.c 2004-10-26 01:00:28.781329296 -0400
@@ -902,6 +902,7 @@
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+#ifdef CONFIG_DNOTIFY
{
.ctl_name = FS_DIR_NOTIFY,
.procname = "dir-notify-enable",
@@ -910,6 +911,7 @@
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+#endif
{
.ctl_name = FS_LEASE_TIME,
.procname = "lease-break-time",

-
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