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[134.134.136.65]) by mx.google.com with ESMTPS id d125si4179224pfd.206.2019.03.03.16.57.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 03 Mar 2019 16:57:32 -0800 (PST) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.65 as permitted sender) client-ip=134.134.136.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.65 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Mar 2019 16:57:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,438,1544515200"; d="scan'208";a="137790581" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by FMSMGA003.fm.intel.com with ESMTP; 03 Mar 2019 16:57:31 -0800 Date: Sun, 3 Mar 2019 08:55:51 -0800 From: Ira Weiny To: Artemy Kovalyov Cc: "john.hubbard@gmail.com" , "linux-mm@kvack.org" , Andrew Morton , LKML , John Hubbard , Jason Gunthorpe , Doug Ledford , "linux-rdma@vger.kernel.org" Subject: Re: [PATCH v2] RDMA/umem: minor bug fix and cleanup in error handling paths Message-ID: <20190303165550.GB27123@iweiny-DESK2.sc.intel.com> References: <20190302032726.11769-2-jhubbard@nvidia.com> <20190302202435.31889-1-jhubbard@nvidia.com> <20190302194402.GA24732@iweiny-DESK2.sc.intel.com> <2404c962-8f6d-1f6d-0055-eb82864ca7fc@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2404c962-8f6d-1f6d-0055-eb82864ca7fc@mellanox.com> User-Agent: Mutt/1.11.1 (2018-12-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Mar 03, 2019 at 11:52:41AM +0200, Artemy Kovalyov wrote: > > > On 02/03/2019 21:44, Ira Weiny wrote: > > > > On Sat, Mar 02, 2019 at 12:24:35PM -0800, john.hubbard@gmail.com wrote: > > > From: John Hubbard > > > > > > ... > > > 3. Dead code removal: the check for (user_virt & ~page_mask) > > > is checking for a condition that can never happen, > > > because earlier: > > > > > > user_virt = user_virt & page_mask; > > > > > > ...so, remove that entire phrase. > > > > > > bcnt -= min_t(size_t, npages << PAGE_SHIFT, bcnt); > > > mutex_lock(&umem_odp->umem_mutex); > > > for (j = 0; j < npages; j++, user_virt += PAGE_SIZE) { > > > - if (user_virt & ~page_mask) { > > > - p += PAGE_SIZE; > > > - if (page_to_phys(local_page_list[j]) != p) { > > > - ret = -EFAULT; > > > - break; > > > - } > > > - put_page(local_page_list[j]); > > > - continue; > > > - } > > > - > > > > I think this is trying to account for compound pages. (ie page_mask could > > represent more than PAGE_SIZE which is what user_virt is being incrimented by.) > > But putting the page in that case seems to be the wrong thing to do? > > > > Yes this was added by Artemy[1] now cc'ed. > > Right, this is for huge pages, please keep it. > put_page() needed to decrement refcount of the head page. You mean decrement the refcount of the _non_-head pages? Ira >