Re: [RFC PATCH] mountinfo: show only reachable mounts

[Jan Blunck <jblunck@suse.de>]

On Tue, 11 Mar 2008 17:17:37 +0100, Miklos Szeredi wrote:

> +/*
> + * 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(&dcache_lock);
> +	for (;;) {
> +		if (dentry == root->dentry && mnt == root->mnt) 
{ +			res = true;
> +			break;
> +		}
> +		if (dentry == mnt->mnt_root || IS_ROOT(dentry)) 
{ +			/* Global root?
> */
> +			spin_lock(&vfsmount_lock);
> +			if (mnt->mnt_parent == mnt) {
> +				spin_unlock(&vfsmount_lock);
> +				break;
> +			}
> +			dentry = mnt->mnt_mountpoint;
> +			mnt = mnt->mnt_parent;
> +			spin_unlock(&vfsmount_lock);
> +			continue;
> +		}
> +		dentry = dentry->d_parent;
> +	}
> +	spin_unlock(&dcache_lock);
> +
> +	return res;
> +}
> +

Hmm, this may hold dcache_lock for some time. Isn't it enough to use 
rcu_readlock() and read_seqbegin(&rename_lock) ?

Cheers,
Jan