Re: [PATCH net-next 3/8] fs/quota: use nla_put_u64_64bit()

From: Jan Kara <jack-AlSwsSmVLrQ@public•gmane.org>
To: Nicolas Dichtel
	<nicolas.dichtel-pdR9zngts4EAvxtiuMwx3w@public•gmane.org>
Cc: dev-yBygre7rU0TnMu66kgdUjQ@public•gmane.org,
	sd-y1jBWg8GRStKuXlAQpz2QA@public•gmane.org,
	netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
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	jhs-jkUAjuhPggJWk0Htik3J/w@public•gmane.org,
	lars.ellenberg-63ez5xqkn6DQT0dZR+AlfA@public•gmane.org,
	jack-IBi9RG/b67k@public•gmane.org,
	johannes-cdvu00un1VgdHxzADdlk8Q@public•gmane.org,
	philipp.reisner-63ez5xqkn6DQT0dZR+AlfA@public•gmane.org,
	davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org,
	kvalo-sgV2jX0FEOL9JmXXK+q4OQ@public•gmane.org,
	drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public•gmane.org
Subject: Re: [PATCH net-next 3/8] fs/quota: use nla_put_u64_64bit()
Date: Tue, 26 Apr 2016 13:08:48 +0200	[thread overview]
Message-ID: <20160426110848.GD27612@quack2.suse.cz> (raw)
In-Reply-To: <1461657978-13360-4-git-send-email-nicolas.dichtel-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>

On Tue 26-04-16 10:06:13, Nicolas Dichtel wrote:
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind•com>

OK, so I somewhat miss a description of what will this do to the netlink
message so that I can judge whether the change is fine for the userspace
counterpart parsing these messages. AFAIU this changes the message format
by adding a QUOTA_NL_A_PAD field before each 64-bit field which needs an
alignment, am I guessing right? Thus when the userspace counterpart uses
genlmsg_parse() it should just silently ignore these attributes if I read
the documentation right. Did I understand this correctly?

								Honza

> ---
>  fs/quota/netlink.c         | 12 +++++++-----
>  include/uapi/linux/quota.h |  1 +
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/quota/netlink.c b/fs/quota/netlink.c
> index d07a2f91d858..8b252673d454 100644
> --- a/fs/quota/netlink.c
> +++ b/fs/quota/netlink.c
> @@ -47,7 +47,7 @@ void quota_send_warning(struct kqid qid, dev_t dev,
>  	void *msg_head;
>  	int ret;
>  	int msg_size = 4 * nla_total_size(sizeof(u32)) +
> -		       2 * nla_total_size(sizeof(u64));
> +		       2 * nla_total_size_64bit(sizeof(u64));
>  
>  	/* We have to allocate using GFP_NOFS as we are called from a
>  	 * filesystem performing write and thus further recursion into
> @@ -68,8 +68,9 @@ void quota_send_warning(struct kqid qid, dev_t dev,
>  	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
>  	if (ret)
>  		goto attr_err_out;
> -	ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
> -			  from_kqid_munged(&init_user_ns, qid));
> +	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
> +				from_kqid_munged(&init_user_ns, qid),
> +				QUOTA_NL_A_PAD);
>  	if (ret)
>  		goto attr_err_out;
>  	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
> @@ -81,8 +82,9 @@ void quota_send_warning(struct kqid qid, dev_t dev,
>  	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
>  	if (ret)
>  		goto attr_err_out;
> -	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
> -			  from_kuid_munged(&init_user_ns, current_uid()));
> +	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
> +				from_kuid_munged(&init_user_ns, current_uid()),
> +				QUOTA_NL_A_PAD);
>  	if (ret)
>  		goto attr_err_out;
>  	genlmsg_end(skb, msg_head);
> diff --git a/include/uapi/linux/quota.h b/include/uapi/linux/quota.h
> index 38baddb807f5..4d2489ef6f10 100644
> --- a/include/uapi/linux/quota.h
> +++ b/include/uapi/linux/quota.h
> @@ -191,6 +191,7 @@ enum {
>  	QUOTA_NL_A_DEV_MAJOR,
>  	QUOTA_NL_A_DEV_MINOR,
>  	QUOTA_NL_A_CAUSED_ID,
> +	QUOTA_NL_A_PAD,
>  	__QUOTA_NL_A_MAX,
>  };
>  #define QUOTA_NL_A_MAX (__QUOTA_NL_A_MAX - 1)
> -- 
> 2.8.1
> 
> 
-- 
Jan Kara <jack@suse•com>
SUSE Labs, CR
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