linux-stable/include/linux/inotify.h
Nick Piggin c32ccd87bf [PATCH] inotify: lock avoidance with parent watch status in dentry
Previous inotify work avoidance is good when inotify is completely unused,
but it breaks down if even a single watch is in place anywhere in the
system.  Robin Holt notices that udev is one such culprit - it slows down a
512-thread application on a 512 CPU system from 6 seconds to 22 minutes.

Solve this by adding a flag in the dentry that tells inotify whether or not
its parent inode has a watch on it.  Event queueing to parent will skip
taking locks if this flag is cleared.  Setting and clearing of this flag on
all child dentries versus event delivery: this is no in terms of race
cases, and that was shown to be equivalent to always performing the check.

The essential behaviour is that activity occuring _after_ a watch has been
added and _before_ it has been removed, will generate events.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Robert Love <rml@novell.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25 08:22:53 -08:00

124 lines
3.9 KiB
C

/*
* Inode based directory notification for Linux
*
* Copyright (C) 2005 John McCutchan
*/
#ifndef _LINUX_INOTIFY_H
#define _LINUX_INOTIFY_H
#include <linux/types.h>
/*
* struct inotify_event - structure read from the inotify device for each event
*
* When you are watching a directory, you will receive the filename for events
* such as IN_CREATE, IN_DELETE, IN_OPEN, IN_CLOSE, ..., relative to the wd.
*/
struct inotify_event {
__s32 wd; /* watch descriptor */
__u32 mask; /* watch mask */
__u32 cookie; /* cookie to synchronize two events */
__u32 len; /* length (including nulls) of name */
char name[0]; /* stub for possible name */
};
/* the following are legal, implemented events that user-space can watch for */
#define IN_ACCESS 0x00000001 /* File was accessed */
#define IN_MODIFY 0x00000002 /* File was modified */
#define IN_ATTRIB 0x00000004 /* Metadata changed */
#define IN_CLOSE_WRITE 0x00000008 /* Writtable file was closed */
#define IN_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */
#define IN_OPEN 0x00000020 /* File was opened */
#define IN_MOVED_FROM 0x00000040 /* File was moved from X */
#define IN_MOVED_TO 0x00000080 /* File was moved to Y */
#define IN_CREATE 0x00000100 /* Subfile was created */
#define IN_DELETE 0x00000200 /* Subfile was deleted */
#define IN_DELETE_SELF 0x00000400 /* Self was deleted */
#define IN_MOVE_SELF 0x00000800 /* Self was moved */
/* the following are legal events. they are sent as needed to any watch */
#define IN_UNMOUNT 0x00002000 /* Backing fs was unmounted */
#define IN_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
#define IN_IGNORED 0x00008000 /* File was ignored */
/* helper events */
#define IN_CLOSE (IN_CLOSE_WRITE | IN_CLOSE_NOWRITE) /* close */
#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* moves */
/* special flags */
#define IN_ONLYDIR 0x01000000 /* only watch the path if it is a directory */
#define IN_DONT_FOLLOW 0x02000000 /* don't follow a sym link */
#define IN_MASK_ADD 0x20000000 /* add to the mask of an already existing watch */
#define IN_ISDIR 0x40000000 /* event occurred against dir */
#define IN_ONESHOT 0x80000000 /* only send event once */
/*
* All of the events - we build the list by hand so that we can add flags in
* the future and not break backward compatibility. Apps will get only the
* events that they originally wanted. Be sure to add new events here!
*/
#define IN_ALL_EVENTS (IN_ACCESS | IN_MODIFY | IN_ATTRIB | IN_CLOSE_WRITE | \
IN_CLOSE_NOWRITE | IN_OPEN | IN_MOVED_FROM | \
IN_MOVED_TO | IN_DELETE | IN_CREATE | IN_DELETE_SELF | \
IN_MOVE_SELF)
#ifdef __KERNEL__
#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/config.h>
#ifdef CONFIG_INOTIFY
extern void inotify_d_instantiate(struct dentry *, struct inode *);
extern void inotify_d_move(struct dentry *);
extern void inotify_inode_queue_event(struct inode *, __u32, __u32,
const char *);
extern void inotify_dentry_parent_queue_event(struct dentry *, __u32, __u32,
const char *);
extern void inotify_unmount_inodes(struct list_head *);
extern void inotify_inode_is_dead(struct inode *);
extern u32 inotify_get_cookie(void);
#else
static inline void inotify_d_instantiate(struct dentry *dentry,
struct inode *inode)
{
}
static inline void inotify_d_move(struct dentry *dentry)
{
}
static inline void inotify_inode_queue_event(struct inode *inode,
__u32 mask, __u32 cookie,
const char *filename)
{
}
static inline void inotify_dentry_parent_queue_event(struct dentry *dentry,
__u32 mask, __u32 cookie,
const char *filename)
{
}
static inline void inotify_unmount_inodes(struct list_head *list)
{
}
static inline void inotify_inode_is_dead(struct inode *inode)
{
}
static inline u32 inotify_get_cookie(void)
{
return 0;
}
#endif /* CONFIG_INOTIFY */
#endif /* __KERNEL __ */
#endif /* _LINUX_INOTIFY_H */