[PATCH] inotify

inotify is intended to correct the deficiencies of dnotify, particularly
its inability to scale and its terrible user interface:

        * dnotify requires the opening of one fd per each directory
          that you intend to watch. This quickly results in too many
          open files and pins removable media, preventing unmount.
        * dnotify is directory-based. You only learn about changes to
          directories. Sure, a change to a file in a directory affects
          the directory, but you are then forced to keep a cache of
          stat structures.
        * dnotify's interface to user-space is awful.  Signals?

inotify provides a more usable, simple, powerful solution to file change
notification:

        * inotify's interface is a system call that returns a fd, not SIGIO.
	  You get a single fd, which is select()-able.
        * inotify has an event that says "the filesystem that the item
          you were watching is on was unmounted."
        * inotify can watch directories or files.

Inotify is currently used by Beagle (a desktop search infrastructure),
Gamin (a FAM replacement), and other projects.

See Documentation/filesystems/inotify.txt.

Signed-off-by: Robert Love <rml@novell.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/include/linux/inotify.h b/include/linux/inotify.h
new file mode 100644
index 000000000000..a40c2bf0408e
--- /dev/null
+++ b/include/linux/inotify.h
@@ -0,0 +1,108 @@
+/*
+ * 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 */
+
+/* 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_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)
+
+#ifdef __KERNEL__
+
+#include <linux/dcache.h>
+#include <linux/fs.h>
+#include <linux/config.h>
+
+#ifdef CONFIG_INOTIFY
+
+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_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 */