[PATCH] inotify: add two inotify_add_watch flags
The below patch lets userspace have more control over the inodes that
inotify will watch. It introduces two new flags.
IN_ONLYDIR -- only watch the inode if it is a directory.
This is needed to avoid the race that can occur when we want to be
sure that we are watching a directory.
IN_DONT_FOLLOW -- don't follow a symlink. In combination
with IN_ONLYDIR we can make sure that we don't watch the target of
symlinks.
The issues the flags fix came up when writing the gnome-vfs inotify
backend. Default behaviour is unchanged.
Signed-off-by: John McCutchan <ttb@tentacle.dhs.org>
Acked-by: Robert Love <rml@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/inotify.c b/fs/inotify.c
index bf7ce1d..2fecb7a 100644
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -364,11 +364,12 @@
/*
* find_inode - resolve a user-given path to a specific inode and return a nd
*/
-static int find_inode(const char __user *dirname, struct nameidata *nd)
+static int find_inode(const char __user *dirname, struct nameidata *nd,
+ unsigned flags)
{
int error;
- error = __user_walk(dirname, LOOKUP_FOLLOW, nd);
+ error = __user_walk(dirname, flags, nd);
if (error)
return error;
/* you can only watch an inode if you have read permissions on it */
@@ -933,6 +934,7 @@
struct file *filp;
int ret, fput_needed;
int mask_add = 0;
+ unsigned flags = 0;
filp = fget_light(fd, &fput_needed);
if (unlikely(!filp))
@@ -944,7 +946,12 @@
goto fput_and_out;
}
- ret = find_inode(path, &nd);
+ if (!(mask & IN_DONT_FOLLOW))
+ flags |= LOOKUP_FOLLOW;
+ if (mask & IN_ONLYDIR)
+ flags |= LOOKUP_DIRECTORY;
+
+ ret = find_inode(path, &nd, flags);
if (unlikely(ret))
goto fput_and_out;
diff --git a/include/linux/inotify.h b/include/linux/inotify.h
index ee5b239..267c88b 100644
--- a/include/linux/inotify.h
+++ b/include/linux/inotify.h
@@ -47,6 +47,8 @@
#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 */