Date: Fri, 10 Sep 2004 14:13:38 +0100 (BST) From: "Brian Somers" <brian@Awfulhak.org> To: "Dima Dorfman" <dd@freebsd.org> Cc: freebsd-net@freebsd.org Subject: Re: uma_zcreate() call from kern_mbuf.c - bug? Message-ID: <42009.192.18.1.9.1094822018.squirrel@192.18.1.9> In-Reply-To: <20040910131030.GB7453@trit.org> References: <20040909214600.12bb5fd5@dev.lan.Awfulhak.org> <20040910131030.GB7453@trit.org>
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> Brian Somers <brian@Awfulhak.org> wrote:
>> Of course m_get() et. al. seem to manage to get MSIZE aligned pointers
>> back
>> from uma_zalloc_arg(zone_mbuf...) anyway, but surely that's an
>> implementation
>> side effect and the align argument should be corrected.
>
> This change looks right to me, but I'm hardly an expert here.
>
>> There should probably also be a KASSERT here to ensure that MSIZE is
>> sane
>
> This might be better as a CTASSERT:
>
> Index: kern_mbuf.c
> ===================================================================
> RCS file: /ref/cvsf/src/sys/kern/kern_mbuf.c,v
> retrieving revision 1.3
> diff -u -r1.3 kern_mbuf.c
> --- kern_mbuf.c 2 Aug 2004 00:18:35 -0000 1.3
> +++ kern_mbuf.c 10 Sep 2004 06:53:10 -0000
> @@ -123,6 +123,9 @@
> static void mb_reclaim(void *);
> static void mbuf_init(void *);
>
> +/* Ensure that MSIZE doesn't break dtom(). */
> +CTASSERT((((MSIZE - 1) ^ MSIZE) + 1) >> 1 == MSIZE);
> +
> /*
> * Initialize FreeBSD Network buffer allocation.
> */
> @@ -135,7 +138,7 @@
> * Configure UMA zones for Mbufs, Clusters, and Packets.
> */
> zone_mbuf = uma_zcreate("Mbuf", MSIZE, mb_ctor_mbuf, mb_dtor_mbuf,
> - NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_MAXBUCKET);
> + NULL, NULL, MSIZE - 1, UMA_ZONE_MAXBUCKET);
> zone_clust = uma_zcreate("MbufClust", MCLBYTES, mb_ctor_clust,
> mb_dtor_clust, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_REFCNT);
> if (nmbclusters > 0)
>
>
Agreed. I didn't know about CTASSERT()!
Cheers.
--
Brian <brian@Awfulhak.org> <brian@[uk.]FreeBSD.org>
<http://www.Awfulhak.org>; <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !
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