From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: [PATCH 10/10] IB: remove the unused usecnt field from struct ib_mr Date: Sun, 20 Dec 2015 11:31:23 +0200 Message-ID: <5676756B.6090208@dev.mellanox.co.il> References: <1450446906-10336-1-git-send-email-hch@lst.de> <1450446906-10336-11-git-send-email-hch@lst.de> <567657D1.5010700@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <567657D1.5010700-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Or Gerlitz , Christoph Hellwig , Doug Ledford , Haggai Eran Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Shani Michaeli List-Id: linux-rdma@vger.kernel.org >> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h >> index 284916d..e45776e 100644 >> --- a/include/rdma/ib_verbs.h >> +++ b/include/rdma/ib_verbs.h >> @@ -1306,7 +1306,6 @@ struct ib_mr { >> u64 iova; >> u32 length; >> unsigned int page_size; >> - atomic_t usecnt; /* count number of MWs */ >> }; > > This comment is part of Roland's uverbs commit. > > I wonder if LL driver supporting the IB_WR_BIND_MW op > ref the MR on port send and deref it on completion? I don't see why any driver would ref the underlying MR at post_send(IB_WR_BIND_MW) time. It doesn't really make sense. However, I think that the patch from Shani 6b52a12bc3fc ("IB/uverbs: Implement memory windows support in uverbs") is wrong. A memory window allocation should really reference the MR and not the PD (which is referenced by the MR). Otherwise the MR deregistration is allowed with windows bound to it. If this is the case then this field is not useless and we should fix ib_uverbs_alloc_mw()? Haggai, can you shed some light here? It's Shani's and your code. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html