On Thu, Sep 05, 2013 at 02:39:11PM +0200, Miklos Szeredi wrote:
> +static bool __has_unlinked_ancestor(struct dentry *dentry)
> +{
> + struct dentry *this;
> +
> + for (this = dentry; !IS_ROOT(this); this = this->d_parent) {
> + int is_unhashed;
> +
> + /* Need exclusion wrt. check_submounts_and_drop() */
> + spin_lock(&this->d_lock);
> + is_unhashed = d_unhashed(this);
> + spin_unlock(&this->d_lock);
> +
> + if (is_unhashed)
> + return true;
> + }
> + return false;
> +}
I still don't get it; why do you need to bother with early setting of
DCACHE_MOUNTED?
You are grabbing rename_lock for write in d_set_mounted(). What kind of races
with check for submounts are you worried about? d_walk() will rescan
everything if something grabs rename_lock for write while it had been running,
so just fold the "have nothing in d_subdir" case of check_submounts_and_drop()
into d_walk() and be done with that... What's the problem with such
variant? AFAICS, all you need to care about is d_set_mounted() not getting
between the scan for submounts and actual __d_drop() and your "finish"
callback is called only after d_walk() having grabbed d_lock *and* rechecked
rename_lock.
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