linux-kernel - Re: [PATCH] Send quota messages via netlink

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Message-ID: <20070903144336.GH7524@duck.suse.cz>
Date:	Mon, 3 Sep 2007 16:43:36 +0200
From:	Jan Kara <jack@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Send quota messages via netlink

On Tue 28-08-07 21:51:28, Andrew Morton wrote:
> On Tue, 28 Aug 2007 16:13:18 +0200 Jan Kara <jack@...e.cz> wrote:
> 
> > +static void send_warning(const struct dquot *dquot, const char warntype)
> > +{
> > +	static unsigned long seq;
> > +	struct sk_buff *skb;
> > +	void *msg_head;
> > +	int ret;
> > +
> > +	skb = genlmsg_new(QUOTA_NL_MSG_SIZE, GFP_NOFS);
> > +	if (!skb) {
> > +		printk(KERN_ERR
> > +		  "VFS: Not enough memory to send quota warning.\n");
> > +		return;
> > +	}
> > +	msg_head = genlmsg_put(skb, 0, seq++, &quota_genl_family, 0, QUOTA_NL_C_WARNING);
> 
> The access to seq is racy, isn't it?
> 
> If so, that can be solved with a lock, or with atomic_add_return().
  Attached is an incremental patch solving the issues you've spotted.
Thanks for review.  The result of the discussion with namespace guys is
that the id used as an identify for filesystem operations should be fine.
If it will ever be something different than a number, we can change the
protocol which should be no problem...
  Also after some more reading, I've found out that we can even easily find
out, which attributes have been sent in the netlink message. So I don't see
a real reason for some versioning of the protocol - either the message has
all the attributes we are interested and then we report it, or it does not
and then we complain that tools are too old and don't understand the
protocol...

									Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs

View attachment "quota-2.6.23-rc4-1-quota_messages_update.diff" of type "text/x-patch" (4775 bytes)