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 73443C3DA49 for ; Thu, 18 Jul 2024 07:05:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EC1306B0082; Thu, 18 Jul 2024 03:05:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E70D36B0083; Thu, 18 Jul 2024 03:05:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D60176B0089; Thu, 18 Jul 2024 03:05:07 -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 B83856B0082 for ; Thu, 18 Jul 2024 03:05:07 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 5A02681995 for ; Thu, 18 Jul 2024 07:05:07 +0000 (UTC) X-FDA: 82351986654.25.CCD23A2 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf06.hostedemail.com (Postfix) with ESMTP id A98DE180016 for ; Thu, 18 Jul 2024 07:05:02 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=FFDPmMlk; spf=none (imf06.hostedemail.com: domain of BATV+8a855cc45d05e91dc6c7+7634+infradead.org+hch@bombadil.srs.infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=BATV+8a855cc45d05e91dc6c7+7634+infradead.org+hch@bombadil.srs.infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1721286265; 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=TiE7IPXDKVwDWy2yLM7UJSm19WTVylqCuLPxGIfuTTM=; b=zi7KXhJHrWB0ovZwo144FPeD0Qy9PXYQiE27BMu7iDVbhPzR3Z90WmfN1wA1w8H0E0eres il/LP3NLHcuFaymPneAxuzU6z8SL4eLoc9mqhoHpuejQoKcm31Z02EPGQQVnupVd0GhVey mhQI6YEe1lLGCbmCHmivKmbMjp2pRLk= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1721286265; a=rsa-sha256; cv=none; b=YAiTY4PqpY907oEqbsstnDSc1uUm0mVGI8ebBYK5w9holMXJ0/vqXDl7+w4WaEi9p/sdeg nf/L9lwPnu/mv5SxtksjwutFs09XtWWNHRY3Nu2yfB9k5w5x8sJgaoD410bLsbdYrt9LKp LsBwdU1B3HYxxCTcw4Vo+e8NP2XaGuA= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=FFDPmMlk; spf=none (imf06.hostedemail.com: domain of BATV+8a855cc45d05e91dc6c7+7634+infradead.org+hch@bombadil.srs.infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=BATV+8a855cc45d05e91dc6c7+7634+infradead.org+hch@bombadil.srs.infradead.org; dmarc=none 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=TiE7IPXDKVwDWy2yLM7UJSm19WTVylqCuLPxGIfuTTM=; b=FFDPmMlk3IXk6WV4UGxaD2gKun Tu7GCtEstwuYGO82DBNMUopJ23CyDaOnwF4/Jd0EK3uBayELDjZ9GsTQ4mKy+cJXcDdqK9sLAq+An yBwUd9T0zn9UVpcdXBcSP8OEb/ZQqBJJTHh+N4seT1YIFYcaEcaUdkVynpDrjTbEd9aTqU2S92z7R VhI09P1FOKLsZ7RfncbgU96/VJimNUwE0b5RzVKN7rTkYEpaL6cSDpa7aA83zF3yWmi2LTmgHyNK2 lBLDPqg8tKAey6Zr3VDXDck2lNPBkRN7qk4PUi+K6infZ1lGFzE8SnTd47qelOfxjRguWs6QW3gCJ uSbvbhtQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sULCA-0000000G5fl-3xu0; Thu, 18 Jul 2024 07:04:54 +0000 Date: Thu, 18 Jul 2024 00:04:54 -0700 From: Christoph Hellwig To: Michal Hocko Cc: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, Barry Song , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL Message-ID: References: <20240717230025.77361-1-21cnbao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: A98DE180016 X-Stat-Signature: k51ikpaw8hz8ap8ipmeqgfqci9sfjmx4 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1721286302-173850 X-HE-Meta: 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 ZNiK2kS8 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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 Thu, Jul 18, 2024 at 08:58:44AM +0200, Michal Hocko wrote: > WARN_ON is effectively BUG_ON with panic_on_warn so if this happens to > be in a user triggerable path then you would have an easy way to panic > the whole machine. It is likely true that the kernel could oops just > right after the failure but that could be recoverable at least. If you set panic_on_warn you are either debugging in which case it's the right thing, or you are fucked. So don't do it unless you expet frequent crashes. > If anything I would just pr_warn with caller address or add dump_stack > to capture the full trace. That would give us the caller that needs > fixing without panicing the system with panic_on_warn. The whole freaking point of __GFP_NOFAIL is that callers don't handle allocation failures. So in fact a straight BUG is the right thing here.