Date: Thu, 01 Mar 2007 13:07:06 +0100 From: Andre Oppermann <andre@freebsd.org> To: "Bruce M. Simpson" <bms@FreeBSD.org> Cc: Bruce M Simpson <bms@incunabulum.net>, net@FreeBSD.org Subject: Re: Proposal: Add M_HASCL(). Message-ID: <45E6C1EA.8030109@freebsd.org> In-Reply-To: <45E6B378.1020703@FreeBSD.org> References: <45E60041.1090607@incunabulum.net> <45E6B378.1020703@FreeBSD.org>
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Bruce M. Simpson wrote: > Bruce M Simpson wrote: >> Much network code needs to know if the mbuf it is looking at is using >> a cluster. I propose putting M_HASCL() in sys/mbuf.h. I realise this >> is a style change, however, it seems to be a very common idiom. > I sent this, then I looked at NetBSD, having caught a glimpse of their > MBUFTRACE code when skimming lots of diffs. That is also a good idea, > and might help us catch problems before they go prime-time; I've added > it to the wiki. > > Point there is, M_HASCL() seems to be a hangover from the 4.4BSD era. > NetBSD seems to treat clusters and external storage as separate > entities. So I'm reconsidering this in the light of this new evidence. > > As far as I understand it, the presence of M_EXT in an mbuf chain's > header in FreeBSD always indicate that we are using external storage > (not necessarily, but possibly, a cluster). > > Can someone confirm this? This is correct. M_EXT is set whenever external storage is attached to an mbuf. We have many different classes of external storage with traditional 2k clusters being one of them. -- Andre
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