From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Blunck <jblunck@suse.de>
Subject: Re: [RFC PATCH] mountinfo: show only reachable mounts
Date: Fri, 14 Mar 2008 16:17:53 +0100
Message-ID: <20080314151753.GB27730@T61>
References: <E1JZ7AX-0003SU-4A@pomaz-ex.szeredi.hu> <fr8la8$si7$1@ger.gmane.org> <E1JZVQk-000664-MC@pomaz-ex.szeredi.hu> <E1JZoUG-0000q7-TV@pomaz-ex.szeredi.hu>
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Cc: linux-fsdevel@vger.kernel.org
To: Miklos Szeredi <miklos@szeredi.hu>
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On Thu, Mar 13, Miklos Szeredi wrote:

> But I'm an idiot.  This is a much simpler and faster implementation
> that uses is_subdir(), which essentially does what you suggested:
> 
> /*
>  * Return true if 'path' is reachable from 'root'
>  */
> static bool is_path_reachable(const struct path *path, const struct path *root)
> {
> 	struct dentry *dentry = path->dentry;
> 	struct vfsmount *mnt = path->mnt;
> 	bool res = false;
> 
> 	spin_lock(&vfsmount_lock);
> 	while (mnt != root->mnt && mnt->mnt_parent != mnt) {
> 		dentry = mnt->mnt_mountpoint;
> 		mnt = mnt->mnt_parent;
> 	}
> 	if (mnt == root->mnt && is_subdir(dentry, root->dentry))
> 		res = true;
> 	spin_unlock(&vfsmount_lock);
> 
> 	return res;
> }

Very well.

BTW, I have a patch rotting in my quilt stack to remove
lives_below_in_same_fs() since is_subdir() provides the same
functionality.

Cheers,
Jan