Messages in this thread | | | Date | Fri, 5 Apr 2013 18:12:20 +0100 | From | Al Viro <> | Subject | Re: [PATCH v2 1/4] dcache: Don't take unnecessary lock in d_count update |
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> @@ -635,22 +640,14 @@ struct dentry *dget_parent(struct dentry *dentry) > { > struct dentry *ret; > > -repeat: > - /* > - * Don't need rcu_dereference because we re-check it was correct under > - * the lock. > - */ > rcu_read_lock(); > - ret = dentry->d_parent; > - spin_lock(&ret->d_lock); > - if (unlikely(ret != dentry->d_parent)) { > - spin_unlock(&ret->d_lock); > - rcu_read_unlock(); > - goto repeat; > - } > + ret = rcu_dereference(dentry->d_parent); > rcu_read_unlock(); > + if (dcount_inc_cmpxchg(ret)) > + return ret; > + spin_lock(&ret->d_lock);
And WTF is going to protect your "ret" from being freed just as you'd done rcu_read_unlock()?
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