> + spin_lock(&mm->page_table_lock);
> + if (mm->hmm) {
> + if (kref_get_unless_zero(&mm->hmm->kref)) {
> + spin_unlock(&mm->page_table_lock);
> + return mm->hmm;
> + }
> + }
> + spin_unlock(&mm->page_table_lock);
This could become:
spin_lock(&mm->page_table_lock);
hmm = mm->hmm
if (hmm && kref_get_unless_zero(&hmm->kref))
goto out_unlock;
spin_unlock(&mm->page_table_lock);
as the last two lines of the function already drop the page_table_lock
and then return hmm. Or drop the "hmm = mm->hmm" asignment above and
return mm->hmm as that should be always identical to hmm at the end
to save another line.
> + /*
> + * The mm->hmm pointer is kept valid while notifier ops can be running
> + * so they don't have to deal with a NULL mm->hmm value
> + */
The comment confuses me. How does the page_table_lock relate to
possibly running notifiers, as I can't find that we take
page_table_lock? Or is it just about the fact that we only clear
mm->hmm in the free callback, and not in hmm_free?
