Date: Fri, 2 Jul 2004 15:13:31 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.org> To: Bosko Milekic <bmilekic@FreeBSD.org> Cc: current@FreeBSD.org Subject: Re: UMA zinit/zctor function error returning Message-ID: <20040702191331.GL1034@green.homeunix.org> In-Reply-To: <20040702184324.GA10170@freefall.freebsd.org> References: <20040702184324.GA10170@freefall.freebsd.org>
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On Fri, Jul 02, 2004 at 06:43:24PM +0000, Bosko Milekic wrote: > > Brian Fundakowski Feldman wrote: > > <URL:http://green.homeunix.org/~green/uma_error_checking.patch>; > > Good work, overall. I've looked at it, here are comments: > > - in mb_ctor_mbuf(), you need to free the mbuf if mac_init_mbuf() > failed, before you return error (SERIOUS). These are the only two places that can call uz_ctor, aren't they? uma_core.c: if (zone->uz_ctor) { if (zone->uz_ctor(item, zone->uz_keg->uk_size, udata, flags) != 0) { uma_zfree_internal(zone, item, udata, SKIP_DTOR); return (NULL); } } ... if (zone->uz_ctor != NULL) { if (zone->uz_ctor(item, keg->uk_size, udata, flags) != 0) { uma_zfree_internal(zone, item, udata, SKIP_DTOR); return (NULL); } } > - return (0) should be "return 0" (STYLE). That's not true according to style(9), even if it looks weird. > - in mb_ctor_pack(), you need to free the mbuf if mac_init_mbuf() > failed, before you return error (SERIOUS). Same as above. > - you didn't make the change for keginit and you split out the > init function types into init (for zones) and keginit (for kegs). > However, keg inits should be able to fail too and it should > probably be the SAME type as the zone init. This is a mistake. > It is especially a mistake since most zones actually use the > keg init, not the zone init (by default). Only if you add > a secondary zone do you get to talk about zone inits. Let me > know if this isn't clear for you. Well, I only did that because there were no places that called for a keg init being used in the first place (no calls to the uma_zone_set_init() function). > - You seem to misunderstand where inits are called. Refer to > my netbuf paper at www.unixdaemons.com/~bmilekic/netbuf_bmilekic.pdf > (specifically the diagrams) to see where the zone init and keg inits > are called; for example, I have no idea why you've now defined > zero_keginit and zero_init, this makes no sense. This part of the > patch (including how you now cast to uma_keginit explicitly in > zone_ctor) needs to be redone. I don't think you should split up > the init types (i.e., zone init and keg init have same types) and > have both of them be able to fail. I know you might find this > tougher since you have to deal with freeing back to the slab from > the keg code on allocation failure, but that complexity is part of > this change's requirement. The only reason for the two zero functions is that one has to return (0), so they have different type signatures. Where do you see a keginit that you would want to be able to fail (or a keginit at all), other than completeness's sake (which isn't really a bad reason). I don't think there is technically any problem now except for changing this for completeness's sake; the only reason there's any cast at all is that the zone constructor is shared between zones and kegs. > - the uma_dbg.c changes call the ctor explicitly from the fini. > I forget the exact reason this is, but now that we're expecting > the ctor to return something, if you are ignoring the return > value, please cast void explicitly here (STYLE). Alternately, > make both keg and zone inits able to fail and propagate the failure, > if any, upwards. I'm not sure what you mean here. There are no return values I see ignored, but a couple functions with similar names (trash_ctor()/mtrash_ctor()). Thanks for taking a look, -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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