[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, 10 insertions, 1 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 5b5f434ac9a0..ce19a2aa0b21 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -61,7 +61,8 @@ enum
         CTL_DEV=7,              /* Devices */
         CTL_BUS=8,              /* Busses */
         CTL_ABI=9,              /* Binary emulation */
-        CTL_CPU=10              /* CPU stuff (speed scaling, etc) */
+        CTL_CPU=10,             /* CPU stuff (speed scaling, etc) */
+        CTL_INOTIFY=11          /* Inotify */
 };
 
 /* CTL_BUS names: */
@@ -70,6 +71,14 @@ enum
         CTL_BUS_ISA=1           /* ISA */
 };
 
+/* CTL_INOTIFY names: */
+enum
+{
+        INOTIFY_MAX_USER_DEVICES=1,     /* max number of inotify device instances per user */
+        INOTIFY_MAX_USER_WATCHES=2,     /* max number of inotify watches per user */
+        INOTIFY_MAX_QUEUED_EVENTS=3     /* Max number of queued events per inotify device instance */
+};
+
 /* CTL_KERN names: */
 enum
 {