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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8A26BCD043F for ; Tue, 6 Jan 2026 06:22:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E99C76B008A; Tue, 6 Jan 2026 01:22:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E1D2C6B0096; Tue, 6 Jan 2026 01:22:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D53226B0098; Tue, 6 Jan 2026 01:22:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id C27766B008A for ; Tue, 6 Jan 2026 01:22:57 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 88FC78B8FA for ; Tue, 6 Jan 2026 06:22:57 +0000 (UTC) X-FDA: 84300545994.06.E59FA01 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf27.hostedemail.com (Postfix) with ESMTP id 03FFC40003 for ; Tue, 6 Jan 2026 06:22:54 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=azKf2pLX; dmarc=pass (policy=none) header.from=infradead.org; spf=none (imf27.hostedemail.com: domain of BATV+478378d1af6c37b4ea59+8171+infradead.org+hch@bombadil.srs.infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=BATV+478378d1af6c37b4ea59+8171+infradead.org+hch@bombadil.srs.infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767680576; a=rsa-sha256; cv=none; b=enJZBbG2e2VzI2eKoYgjqYGsT7oIE5m8mAqHL76ShoJ1lwrOftx/IpjhJVNoPha12uPd8r ER65bpDIgZ3W6cNLBS80hqtpjxrzZvIo5U7vJYLY2SI6l3S2X/WETNBg8SGPHbOsS7US0v od3aOKmfVaHut+B8WczUOUJj1KWi7oY= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=azKf2pLX; dmarc=pass (policy=none) header.from=infradead.org; spf=none (imf27.hostedemail.com: domain of BATV+478378d1af6c37b4ea59+8171+infradead.org+hch@bombadil.srs.infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=BATV+478378d1af6c37b4ea59+8171+infradead.org+hch@bombadil.srs.infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767680576; 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=NMGvj2UYTxDIhlojRUGlaXmNgk7jzB5FqEZJYNIzHEk=; b=OsL8j+2GXlI/I1G4fnlVEQkAbJrLwuJ+mlCrQineGDpUtT+iVAi01y76cylGNRubHbJFKC F2Q0fBtosJSTTsLkyIZKTq6w3cj99up8iEchXNGKgpaomb4nN1xgrD88DnD53RMKFhkJ7+ EaVDS18dJoprXrMC2oLvlhmnjKVY/Ls= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=NMGvj2UYTxDIhlojRUGlaXmNgk7jzB5FqEZJYNIzHEk=; b=azKf2pLXG1AFtApEQlzeWkYSfj RBOoYwUZAYaJHmTlnmnH1e5aKg6k0alXBYfudiV1SxhBp4r51GrVNqYqQGFTpTUtr1FeviBAX7aoB Udr8s4JK1xndy7zIWfKVqGz6jUyZQIVdGnk2mEj/ixSXhDdWq4EtLkENBpmT0dV/nQE3CGZnHvvVs HpHXRPIPLbbo6yK92RbYsSC5iC8lugbrd2q5+SXHO2hYwBGXgPkOJZr14GTdahIZ72rQhi84+OIn9 Ewpu2fTMSpsOh+rNhegKi7trQf+GfV/ycnzm/T+FU+tFNx4054y+ledcIWA0Rf8NRpoWE7EhwBB1o gdllpJhQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vd0Sz-0000000CSwm-0wkQ; Tue, 06 Jan 2026 06:22:53 +0000 Date: Mon, 5 Jan 2026 22:22:53 -0800 From: Christoph Hellwig To: Vlastimil Babka Cc: klourencodev@gmail.com, linux-mm@kvack.org, Christoph Hellwig , akpm@linux-foundation.org Subject: Re: [PATCH] mm/mempool.c: set @elems slots to NULL once freed Message-ID: References: <20251223231054.16061-1-klourencodev@gmail.com> <07c4f991-ae41-456d-8e7f-287bf8676c9e@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07c4f991-ae41-456d-8e7f-287bf8676c9e@suse.cz> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 03FFC40003 X-Stat-Signature: 8ksqq6ckyyhrbn7b8kcdrzwx88jyrz3o X-HE-Tag: 1767680574-76259 X-HE-Meta: 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 /6IUtiU1 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 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, Jan 05, 2026 at 05:46:47PM +0100, Vlastimil Babka wrote: > On 12/24/25 00:10, klourencodev@gmail.com wrote: > > From: Kevin Lourenco > > > > This is documented in the function comment as "...and sets their > > slots in @elems to NULL.", but it was not followed. > > > > We need to follow the NULL assignment, because elements newly returned > > to the pool must not be touched under any circumstances by the user. > > Well alternatively we could update the comment if no user needs to rely on > this. Since it was modeled after __alloc_pages_bulk()/release_pages() and > release_pages() doesn't do this, we could also avoid it for perf reasons. > Christoph, what do you think? Not sure. I hate the magic null skipping behavior in __alloc_pages_bulk()/release_pages(), but given that we try to stay compatible it might be best to do this.