Commit 8140a500 authored by John McCutchan's avatar John McCutchan Committed by Linus Torvalds
Browse files

[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: default avatarJohn McCutchan <ttb@tentacle.dhs.org>
Acked-by: default avatarRobert Love <rml@novell.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b4788f6d

fs/inotify.c

+10 −3
Original line number Diff line number Diff line
@@ -364,11 +364,12 @@ static int inotify_dev_get_wd(struct inotify_device *dev, 
/*

 * 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 @@ asmlinkage long sys_inotify_add_watch(int fd, const char __user *path, u32 mask) 
	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 @@ asmlinkage long sys_inotify_add_watch(int fd, const char __user *path, u32 mask) 
		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;

include/linux/inotify.h

+2 −0
Original line number Diff line number Diff line
@@ -47,6 +47,8 @@ struct inotify_event { 
#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 */

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