Date: Fri, 10 Sep 2004 13:10:31 +0000 From: Dima Dorfman <dd@freebsd.org> To: Brian Somers <brian@Awfulhak.org> Cc: freebsd-net@freebsd.org Subject: Re: uma_zcreate() call from kern_mbuf.c - bug? Message-ID: <20040910131030.GB7453@trit.org> In-Reply-To: <20040909214600.12bb5fd5@dev.lan.Awfulhak.org> References: <20040909214600.12bb5fd5@dev.lan.Awfulhak.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)
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