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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id c1si16469397plr.405.2019.07.08.10.35.41 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 08 Jul 2019 10:35:41 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@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=oIfcgycO; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@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=n9fo3wNw7aw0RbIvRpzphALTB15Qd7wOzZ709YJZYuY=; b=oIfcgycOcXRvCrTXgzSUV3Bbf KxQgqOLbwzHQGVNcZ7LSDii9CxBNLC5dofvJT19StoJNVlTzLJeQMrZ4MDiLx8JWqU9/dAlS8j4rs x3Cjiih3NScNZa19n6elIHzrcKQNF/BnylzXlnLZ6FbTZCo0oVYG5LuOfOj3yMH5DmF5nlBBi/lCi QKu8WOzXkvlFv4ag30R/h4cbVeI3BCx11EqJI5VVi7aT+6gD0MS493/D0mhY+otM0exYLPWc79BJ4 5/ffMw6ehL1nj9mt8Yo3CRY11wQVVZ6ZR3lTUgVce2PL8EKpnd2GtWPjkUGTpACd3m3/PQudvUw6z n0VyKrmZA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hkXY6-0006it-Eo; Mon, 08 Jul 2019 17:35:34 +0000 Date: Mon, 8 Jul 2019 10:35:34 -0700 From: Matthew Wilcox To: Pengfei Li Cc: akpm@linux-foundation.org, urezki@gmail.com, rpenyaev@suse.de, peterz@infradead.org, guro@fb.com, rick.p.edgecombe@intel.com, rppt@linux.ibm.com, aryabinin@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmalloc.c: Remove always-true conditional in vmap_init_free_space Message-ID: <20190708173534.GF32320@bombadil.infradead.org> References: <20190708170631.2130-1-lpf.vector@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190708170631.2130-1-lpf.vector@gmail.com> User-Agent: Mutt/1.11.4 (2019-03-13) 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 Tue, Jul 09, 2019 at 01:06:31AM +0800, Pengfei Li wrote: > When unsigned long variables are subtracted from one another, > the result is always non-negative. > > The vmap_area_list is sorted by address. > > So the following two conditions are always true. > > 1) if (busy->va_start - vmap_start > 0) > 2) if (vmap_end - vmap_start > 0) > > Just remove them. That condition won't be true if busy->va_start == vmap_start.