From: John McCutchan Date: Mon, 12 Dec 2005 08:37:14 +0000 (-0800) Subject: [PATCH] inotify: add two inotify_add_watch flags X-Git-Tag: firefly_0821_release~38603^2~151 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8140a5005bc6f1c9d0fa103460d50d472e6e3426;p=firefly-linux-kernel-4.4.55.git [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 Acked-by: Robert Love Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/inotify.c b/fs/inotify.c index bf7ce1d2412b..2fecb7af4a77 100644 --- a/fs/inotify.c +++ b/fs/inotify.c @@ -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; diff --git a/include/linux/inotify.h b/include/linux/inotify.h index ee5b239092ed..267c88b5f742 100644 --- a/include/linux/inotify.h +++ b/include/linux/inotify.h @@ -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 */