From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E1B7C77B75 for ; Mon, 8 May 2023 21:13:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C28FA6B0083; Mon, 8 May 2023 17:13:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BD97D6B0085; Mon, 8 May 2023 17:13:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AA0B2900002; Mon, 8 May 2023 17:13:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 97D296B0083 for ; Mon, 8 May 2023 17:13:39 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0E9E11A031E for ; Mon, 8 May 2023 21:13:39 +0000 (UTC) X-FDA: 80768339358.20.9FA0F0A Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf11.hostedemail.com (Postfix) with ESMTP id B8AD54000A for ; Mon, 8 May 2023 21:13:36 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Bm/xNlf3"; spf=none (imf11.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1683580417; a=rsa-sha256; cv=none; b=2oOPyThFXoHah3nOBMKoAt5EV8yWEHYnD+F+Cr2bOw4cavX792HxQBJCiOfKuNZ84i0XSl 1DUnJjz/Xb+SouAA51ni3Vl4yFTKCbch3bojr0y2n2eTGRG9TB71pjA9j1LLD5NBHujpzO A9mTu2Eod/dst2RvrT9Dqra6IHjPHRY= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="Bm/xNlf3"; spf=none (imf11.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1683580417; 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:dkim-signature; bh=XOfR5eYqFEKI2MRwh9rMh2Y6eXpYj1Cs8OGL6W+hOOw=; b=Wkkn+I/xs66Td4VDv5tlQ2RKYll0Six94ZCyAkGybwGEy7EOYN4ooe6cY4nMSWt42+bJR7 LmuQiLwIlv/kwtiNZOg7UOObioh7PXQZxeqZJ8spVt22iax2M9N3MzmEh8QTLptj3ADKcd QV+cbqnZwkjbVJsJ7+YtdPISlXsw9uk= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=XOfR5eYqFEKI2MRwh9rMh2Y6eXpYj1Cs8OGL6W+hOOw=; b=Bm/xNlf3ZvZys8QuPJvX+zIHtq nF7j97jCosW8FystIsyTQ2INw9EuyYHCOMjd0w0y4cHC1w4p2Q3eld5ffdWccgKcxN25CqvmXcyX3 GXBRoOWKV86rvccyT20Y5M6fzHNguYjaRRogHBoWLr+LYfy7LIMoVtZJS4/WNjFvYM0hEurjjH6PK nD0FQ3QV0HxQZFkq2DxuuAKw2xcxd1+wohoCZQAwpbkRjjDc3nURzC5YjHSF31vV1/2g9Fr4+UdbK zKkg9wTCiPdjauQBSjjV07j+E7LFLkFeqGdXcxq3tm0G350ZAg+UA8e6jm0VrDbAhZAjiS8uyiH7S B6LBVoqA==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pw8Ah-00EVH7-AR; Mon, 08 May 2023 21:13:27 +0000 Date: Mon, 8 May 2023 22:13:27 +0100 From: Matthew Wilcox To: Theodore Ts'o Cc: Tudor Ambarus , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, joneslee@google.com, linux-mm@kvack.org Subject: Re: [PATCH] ext4: remove superfluous check that pointer is not NULL Message-ID: References: <20230508151337.79304-1-tudor.ambarus@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: n9xcrrm96gpd8hpj56jfct8q6g76gngx X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B8AD54000A X-HE-Tag: 1683580416-626193 X-HE-Meta: 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 BDIy09C6 Lsrmxyyk37mdEx9NPNzfKBoLZW7ou9/XJS37tCU7NZ2UX03DFm3nqzvIDZu1F9G8Gvh5GGHKKebef1emALs+JDeJ62VtDA7fqP01s0OHHwt3IfT/sOZJnihDHou42ZW2NjY+LknVxyyJc5mWMDDB6V/iMBv6soiyELSwsXrFCNz24FXTKq6rP80b4wwK3eJSxvsLq 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 Mon, May 08, 2023 at 12:14:54PM -0400, Theodore Ts'o wrote: > On Mon, May 08, 2023 at 03:13:37PM +0000, Tudor Ambarus wrote: > > If @buffer is NULL, no operation is performed for kvfree(buffer), > > remove superfluous check. > > > > Signed-off-by: Tudor Ambarus > > I was looking at this just a few weeks ago, and I couldn't find any > actual *documentation* that it was safe to call vfree(NIILL) or > kvfree(NULL). The problem is there are a lot of architecture-specific > functions, and unlike with kfree() there is no top-level "if (ptr == > NULL) return;" in the top-level vfree() and kvfree(). There doesn't need to be in kvfree(). is_vmalloc_addr() returns 'false' for NULL, so it calls kfree(), which as you note has an explicit check for ZERO_OR_NULL_PTR(). is_vmalloc_addr() also returns false for the ZERO pointer, fwiw. I agree that this should be explicitly documented as allowed, since it's not reasonable to expect users to dig through these functions to verify that such a change is safe.