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[198.145.29.99]) by mx.google.com with ESMTPS id d10si3515082pla.42.2019.03.06.21.46.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Mar 2019 21:46:07 -0800 (PST) Received-SPF: pass (google.com: domain of jikos@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=JnpI9P7J; spf=pass (google.com: domain of jikos@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=jikos@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from pobox.suse.cz (prg-ext-pat.suse.com [213.151.95.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 47BE920835; Thu, 7 Mar 2019 05:46:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551937566; bh=woS8eJdF9WhN4ajNoBXAip9dtR/2dJRhAAKFISudxNA=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=JnpI9P7JZvwsGbKHOcx2/JGhPR4vyJd/ZcnCjfwjYyMtNLhlCRy9CwMVhuNuQC9jZ k+M7DQS2Z6GhDz7L7A7ychx/sNNQ7Uj8dW/doLFzVkZazEc8s7GKodp1OXF6z717H+ lA8f3sfTnF8sP3Dj2+wfATWll6jNd1aOxje5dJiQ= Date: Thu, 7 Mar 2019 06:46:00 +0100 (CET) From: Jiri Kosina To: Dominique Martinet cc: Andrew Morton , Vlastimil Babka , Linus Torvalds , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Peter Zijlstra , Greg KH , Jann Horn , Andy Lutomirski , Dave Chinner , Kevin Easton , Matthew Wilcox , Cyril Hrubis , Tejun Heo , "Kirill A . Shutemov" , Daniel Gruss Subject: Re: [PATCH 1/3] mm/mincore: make mincore() more conservative In-Reply-To: <20190307004036.GA16785@nautica> Message-ID: References: <20190130124420.1834-1-vbabka@suse.cz> <20190130124420.1834-2-vbabka@suse.cz> <20190306151351.f8ae1acae51ccad1a3537284@linux-foundation.org> <20190307004036.GA16785@nautica> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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 Thu, 7 Mar 2019, Dominique Martinet wrote: > > > > > > addr = 4095 > > > vma->vm_end = 4096 > > > pages = 1000 > > > > > > then `end' is 4096 and `(end - addr) << PAGE_SHIFT' is zero, but it > > > should have been 1. > > > > Good catch! It should rather be something like > > > > unsigned long pages = (end >> PAGE_SHIFT) - (addr >> PAGE_SHIFT); > > That would be 0 for addr = 0 and vma->vm_end = 1; I assume we would > still want to count that as one page. Yeah, that was bogus as well, ETOOTIRED yesterday, sorry for the noise. Both the variants are off. > I'm not too familiar with this area of the code, but I think there's a > handy macro we can use for this, perhaps > DIV_ROUND_UP(end - addr, PAGE_SIZE) ? > > kernel/kexec_core.c has defined PAGE_COUNT() which seems more > appropriate but I do not see a global equivalent > #define PAGE_COUNT(x) (((x) + PAGE_SIZE - 1) >> PAGE_SHIFT) I'll fix that up when doing the other changes requested by Andrew. Thanks, -- Jiri Kosina SUSE Labs