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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id o6si5289163plh.197.2019.06.15.07.17.32 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sat, 15 Jun 2019 07:17:32 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of batv+78a6abdb7ec5759febfc+5774+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=ZGV0NCi9; spf=pass (google.com: best guess record for domain of batv+78a6abdb7ec5759febfc+5774+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+78a6abdb7ec5759febfc+5774+infradead.org+hch@bombadil.srs.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=RsiIOe9hz9lv0grh/5TETFa2K+PcFkUA7+fv86fOR5Y=; b=ZGV0NCi9ysO0XtRDFkLleOXhx Pytm+wwoUaqIyplTuPpzPx/Um5MRpO7oD21ESdm15ZuobrU5ByqxevsIgAb+esf98ncN5O3TO/gi5 ngxJcin5B8yz8EStFibw7qlVy26TuST04itrGnYArJ0P8gvRWor6jkiZgOlB+tIDErzLL5J8u9E5G 3B+q8ub4IIQvi1S4JxhxHCfMFg14viWDC3mbn+ho1Uuql4o+caakGrzhtD/njve0bkvHan7V4u1hb VHQQPTjV8xX35xtkkXqXRC6KHzFfG6KaCEfn4GZ5MW//F208juEbvZsLmv9LYpKHc8f3ys425dOWH Ta35tRB7Q==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hc9Ul-0004Sq-0D; Sat, 15 Jun 2019 14:17:27 +0000 Date: Sat, 15 Jun 2019 07:17:26 -0700 From: Christoph Hellwig To: Jason Gunthorpe Cc: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Ben Skeggs , Jason Gunthorpe , Souptick Joarder , Ira Weiny , Philip Yang Subject: Re: [PATCH v3 hmm 09/12] mm/hmm: Poison hmm_range during unregister Message-ID: <20190615141726.GI17724@infradead.org> References: <20190614004450.20252-1-jgg@ziepe.ca> <20190614004450.20252-10-jgg@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190614004450.20252-10-jgg@ziepe.ca> User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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: > - /* Sanity check this really should not happen. */ > - if (hmm == NULL || range->end <= range->start) > - return; > - > mutex_lock(&hmm->lock); > list_del_rcu(&range->list); > mutex_unlock(&hmm->lock); > > /* Drop reference taken by hmm_range_register() */ > - range->valid = false; > mmput(hmm->mm); > hmm_put(hmm); > - range->hmm = NULL; > + > + /* > + * The range is now invalid and the ref on the hmm is dropped, so > + * poison the pointer. Leave other fields in place, for the caller's > + * use. > + */ > + range->valid = false; > + memset(&range->hmm, POISON_INUSE, sizeof(range->hmm)); Formatting seems to be messed up. But again I don't see the value in the poisoning, just let normal linked list debugging do its work. The other cleanups looks fine to me.