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[209.85.220.65]) by mx.google.com with SMTPS id i17sor3638866oik.92.2019.07.08.10.58.11 for (Google Transport Security); Mon, 08 Jul 2019 10:58:11 -0700 (PDT) Received-SPF: pass (google.com: domain of lpf.vector@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Kn+ywXAH; spf=pass (google.com: domain of lpf.vector@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=lpf.vector@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=J6BYXR7+fOdaYBcbsh3ughBec33Q5ZK6pIAnMm20zX4=; b=Kn+ywXAHUiDPK5+TJCW6kotSSgpd2BHUDV/2hUkPZNa+N4r5coXiFuu3l6K3D1Zbwj FI9bcHWA1ajVrR3Y0W6Xix4ewCKitv2pdqvT1+r1V7z72PVfPoRnL84Euav+NXe19qT4 rODKJZieMLdDEq4CRj7FZ4/qJRAduZpTAFy697lgHDkcdIi0A2biKe3/IuvACWtpEJ3G Mg54FTPHln+5J8ONLpPXf6a0oVi1rYUU6poMXe1I2pCulaFXMsEWq2Cl5zVGjyCoCpiY i5TEN97zqBk2QVfWX0w/bn/A8w0ZSYvne/1WI777j8ypcyqwQ3zrUNeBVZsLeYWnTF46 cEog== X-Google-Smtp-Source: APXvYqzFB5NdeTU13L7Fv1wsmPdbONbYZrMIHrL7iJKHItGJ2/5APvUtcBxAYOTpZCxb/9YdP2bFcEtzFfvwSBY3QTo= X-Received: by 2002:aca:4d12:: with SMTP id a18mr10154747oib.33.1562608690964; Mon, 08 Jul 2019 10:58:10 -0700 (PDT) MIME-Version: 1.0 References: <20190708170631.2130-1-lpf.vector@gmail.com> <20190708173534.GF32320@bombadil.infradead.org> In-Reply-To: <20190708173534.GF32320@bombadil.infradead.org> From: Pengfei Li Date: Tue, 9 Jul 2019 01:57:59 +0800 Message-ID: Subject: Re: [PATCH] mm/vmalloc.c: Remove always-true conditional in vmap_init_free_space To: Matthew Wilcox Cc: akpm@linux-foundation.org, Uladzislau Rezki , 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 Content-Type: text/plain; charset="UTF-8" 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 9, 2019 at 1:35 AM Matthew Wilcox wrote: > > 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. Yes, you're right. Sorry for my bad job.