From: Al Viro <viro@ZenIV.linux.org.uk>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Jeff Layton <jlayton@redhat.com>,
Miklos Szeredi <mszeredi@suse.cz>, Ian Kent <raven@themaw.net>,
Sage Weil <sage@inktank.com>, Steve French <sfrench@samba.org>,
Trond Myklebust <Trond.Myklebust@netapp.com>,
Eric Paris <eparis@redhat.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
autofs@vger.kernel.org, ceph-devel@vger.kernel.org,
linux-cifs@vger.kernel.org, samba-technical@lists.samba.org,
linux-nfs@vger.kernel.org, "Chandramouleeswaran,
Aswin" <aswin@hp.com>, "Norton, Scott J" <scott.norton@hp.com>,
Andi Kleen <andi@firstfloor.org>,
Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH v2 1/4] dcache: Don't take unnecessary lock in d_count update
Date: Fri, 5 Apr 2013 18:12:20 +0100 [thread overview]
Message-ID: <20130405171220.GD4068@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1365181061-30787-2-git-send-email-Waiman.Long@hp.com>
> @@ -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()?
next prev parent reply other threads:[~2013-04-05 17:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-05 16:57 [PATCH v2 0/4] dcache: make dcache more scalable on large system Waiman Long
2013-04-05 16:57 ` [PATCH v2 1/4] dcache: Don't take unnecessary lock in d_count update Waiman Long
2013-04-05 17:12 ` Al Viro [this message]
[not found] ` <20130405171220.GD4068-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2013-04-05 20:26 ` Waiman Long
2013-04-05 16:57 ` Waiman Long
2013-04-05 16:57 ` [PATCH RFC v2 2/4] dcache: introduce a new sequence read/write lock type Waiman Long
[not found] ` <1365181061-30787-1-git-send-email-Waiman.Long-VXdhtT5mjnY@public.gmane.org>
2013-04-05 16:57 ` Waiman Long
2013-04-05 16:57 ` [PATCH v2 4/4] dcache: don't need to take d_lock in prepend_path() Waiman Long
2013-04-05 16:57 ` [PATCH v2 RFC 3/4] dcache: change rename_lock to a sequence read/write lock Waiman Long
2013-04-05 16:57 ` Waiman Long
2013-04-05 16:57 ` [PATCH v2 4/4] dcache: don't need to take d_lock in prepend_path() Waiman Long
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