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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740398598; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+ryFhl8+XSjDn6mgJa7GSQexAYqewTfKXy0rTXVoLUU=; b=8hw1V499nU58ThMy8RVFeWk67zVxV8Q/Mh2FuJajCGJDRpJGiYxoM8SUq5QQUdXvq5O9gZ Fte5q/BhkaErBnr7HDiAFjyKMChZhJqu96ok/sF3WiffIaScjvR5Qw+GV0fxM44QwLeepy dHyVK+b25XbNalvOW1Dv7Wu2eJsBaCQ= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 6CDB15C62FE; Mon, 24 Feb 2025 12:02:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8AA39C4CED6; Mon, 24 Feb 2025 12:03:14 +0000 (UTC) Date: Mon, 24 Feb 2025 12:03:12 +0000 From: Catalin Marinas To: Ryan Roberts Cc: Will Deacon , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Alexandre Ghiti , Kevin Brodsky , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 08/14] mm/vmalloc: Warn on improper use of vunmap_range() Message-ID: References: <20250217140809.1702789-1-ryan.roberts@arm.com> <20250217140809.1702789-9-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250217140809.1702789-9-ryan.roberts@arm.com> X-Rspam-User: X-Rspamd-Queue-Id: 6109840006 X-Rspamd-Server: rspam12 X-Stat-Signature: o4mcm996q578wh8jg7tzd6yh3nx81sda X-HE-Tag: 1740398598-957572 X-HE-Meta: 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 6rEVPe5c u2nX8nUQg0/5Os2RUv898xGX3KMuIMMTS9dB7+oSJR9ORSviMes0oCi8j/gNr+HHynaVzUMYXQCaM7jKG4ElurSb8QdfEjQTzJGxAJP7DwfXWsO4rm7wt5oEu0sjKhXXlrxqHn6ZgcZOeQLjR3HJAKk3UZl+zfg39OXyIFnJ9NEcTQbMxHSdQKfjExPfsvTjiUbk+IKWXGMUywR+bTCeV/fdQ8KDnU9Hz9y2pE2Sqq9e7eDDK7KHIhWXLUj5hrzrtu/9D1UZLU6ZPoIl90JGLg4LiKJ1B7rXvVWz3OjKXc+UXT8FTm8WLzbZNHVRXaOjoNHouI9A+59vay1qXdil5IclgQU+F+ft6BbuD1de/yuntHsi9ucMC8wkmNCWVyxYUWnWK+pjXeES5nwsoIe6AugFHa9BV0UCVErt0Z4vqeAT+5mAEgHnhIKIaP971vSAxZIm3ZWhFp0qwcF0= 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: List-Subscribe: List-Unsubscribe: On Mon, Feb 17, 2025 at 02:08:00PM +0000, Ryan Roberts wrote: > A call to vmalloc_huge() may cause memory blocks to be mapped at pmd or > pud level. But it is possible to subsequently call vunmap_range() on a > sub-range of the mapped memory, which partially overlaps a pmd or pud. > In this case, vmalloc unmaps the entire pmd or pud so that the > no-overlapping portion is also unmapped. Clearly that would have a bad > outcome, but it's not something that any callers do today as far as I > can tell. So I guess it's just expected that callers will not do this. > > However, it would be useful to know if this happened in future; let's > add a warning to cover the eventuality. > > Signed-off-by: Ryan Roberts Reviewed-by: Catalin Marinas