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From: Johannes Berg <johannes@sipsolutions.net>
To: Taehee Yoo <ap420073@gmail.com>
Cc: "David Miller" <davem@davemloft.net>,
	Netdev <netdev@vger.kernel.org>,
	linux-wireless@vger.kernel.org,
	"Jakub Kicinski" <jakub.kicinski@netronome.com>,
	j.vosburgh@gmail.com, vfalico@gmail.com,
	"Andy Gospodarek" <andy@greyhouse.net>,
	"Jiří Pírko" <jiri@resnulli.us>,
	sd@queasysnail.net, "Roopa Prabhu" <roopa@cumulusnetworks.com>,
	saeedm@mellanox.com, manishc@marvell.com, rahulv@marvell.com,
	kys@microsoft.com, haiyangz@microsoft.com,
	"Stephen Hemminger" <stephen@networkplumber.org>,
	sashal@kernel.org, hare@suse.de, varun@chelsio.com,
	ubraun@linux.ibm.com, kgraul@linux.ibm.com,
	"Jay Vosburgh" <jay.vosburgh@canonical.com>,
	"Cody Schuffelen" <schuffelen@google.com>,
	bjorn@mork.no
Subject: Re: [PATCH net v4 01/12] net: core: limit nested device depth
Date: Tue, 01 Oct 2019 15:57:05 +0200	[thread overview]
Message-ID: <9bbf73e318df17d179014937cb6c1335fb303611.camel@sipsolutions.net> (raw)
In-Reply-To: <CAMArcTW6q=ga1juv_Qp-dKwRwxneAEsX4xQxN-n19oWM-VUQ+w@mail.gmail.com> (sfid-20191001_155348_267769_C0F821E2)

Hi,

(jumping out now, forgive me for being so brief)

> If I understand correctly, you said about the alignment of
> "lower_level" and "upper_level".
> I thought this place is a fine position for variables as regards the
> alignment and I didn't try to put each variable in different places.
> 
> If I misunderstood your mention, please let me know.

Not sure what you mean, alignment doesn't matter for them (they're u8).

I was thinking of the packing for the overall struct, we have:

        unsigned int            max_mtu;
        unsigned short          type;
        unsigned short          hard_header_len;
        unsigned char           min_header_len;

+	unsigned char		upper_level, lower_level;

        unsigned short          needed_headroom;
        unsigned short          needed_tailroom;


Previously, there was a one byte hole at that spot due to a single
"unsigned char" (after something aligned at least 4 bytes) followed by
"unsigned short" - now you push that out a bit.

If you place the variables a bit lower, below "name_assign_type", you
probably fill a hole instead.

Check out the 'pahole' tool.

johannes


  reply	other threads:[~2019-10-01 13:57 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-28 16:48 [PATCH net v4 00/12] net: fix nested device bugs Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 01/12] net: core: limit nested device depth Taehee Yoo
2019-09-28 19:36   ` Johannes Berg
2019-09-29 11:05     ` Taehee Yoo
2019-10-01  7:11       ` Johannes Berg
2019-10-01 13:53         ` Taehee Yoo
2019-10-01 13:57           ` Johannes Berg [this message]
2019-10-01 18:23             ` Taehee Yoo
2019-10-10 10:19   ` Sabrina Dubroca
2019-10-12 11:42     ` Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 02/12] vlan: use dynamic lockdep key instead of subclass Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 03/12] bonding: fix unexpected IFF_BONDING bit unset Taehee Yoo
2019-09-30 20:48   ` Jay Vosburgh
2019-09-28 16:48 ` [PATCH net v4 04/12] bonding: use dynamic lockdep key instead of subclass Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 05/12] team: use dynamic lockdep key instead of static key Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 06/12] macsec: use dynamic lockdep key instead of subclass Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 07/12] macvlan: " Taehee Yoo
2019-09-28 19:14   ` Johannes Berg
2019-09-29  8:03     ` Taehee Yoo
2019-10-01  7:25       ` Johannes Berg
2019-10-05  9:13         ` Taehee Yoo
2019-10-07 11:41           ` Johannes Berg
2019-10-08  8:13             ` Taehee Yoo
2019-10-21 16:00             ` Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 08/12] macsec: fix refcnt leak in module exit routine Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 09/12] net: core: add ignore flag to netdev_adjacent structure Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 10/12] vxlan: add adjacent link to limit depth level Taehee Yoo
2019-09-28 16:48 ` [PATCH net v4 11/12] net: remove unnecessary variables and callback Taehee Yoo
2019-09-28 19:42   ` Johannes Berg
2019-09-28 16:48 ` [PATCH net v4 12/12] virt_wifi: fix refcnt leak in module exit routine Taehee Yoo
2019-09-28 18:57   ` Johannes Berg
2019-10-07 11:22   ` Sabrina Dubroca
2019-10-08  6:53     ` Taehee Yoo
2019-09-28 19:20 ` [PATCH net v4 00/12] net: fix nested device bugs Johannes Berg
2019-09-29  8:31   ` Taehee Yoo
2019-10-01  7:39     ` Johannes Berg
2019-10-05  9:40       ` Taehee Yoo

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