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 7BBA2C6FA82 for ; Fri, 23 Sep 2022 14:54:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E4E9380008; Fri, 23 Sep 2022 10:54:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DFE5B80007; Fri, 23 Sep 2022 10:54:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CC63180008; Fri, 23 Sep 2022 10:54:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B983180007 for ; Fri, 23 Sep 2022 10:54:12 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 99267C0A1D for ; Fri, 23 Sep 2022 14:54:12 +0000 (UTC) X-FDA: 79943645544.29.26176A7 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [193.142.43.52]) by imf13.hostedemail.com (Postfix) with ESMTP id E3F9320011 for ; Fri, 23 Sep 2022 14:54:11 +0000 (UTC) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1obk49-0005kN-E1; Fri, 23 Sep 2022 16:54:09 +0200 Date: Fri, 23 Sep 2022 16:54:09 +0200 From: Florian Westphal To: Uladzislau Rezki Cc: Florian Westphal , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, vbabka@suse.cz, akpm@linux-foundation.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, Martin Zaharinov Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC Message-ID: <20220923145409.GF22541@breakpoint.cc> References: <20220923103858.26729-1-fw@strlen.de> <20220923133512.GE22541@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663944852; 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=6t7Bzb59KeLBu2JN1j2i5iXwKUjEPZWQCnmP5RXLr9E=; b=FDqXCv/vMA1MTbw1DJ+6jsaDd1Kk2lG+/WgCDf2usdwBaOTJvGebOCVE77ejfh5mT1TXFG i65hgET0IK9F8K0i0kPE5ldBoSQa6+VVOEzAGlUJ6tNtloDb/IMI3ByaitATRVVOV+E/ae GLLb2Gm8Q/SvhTSUbjzctZGPnXGicc4= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf13.hostedemail.com: domain of fw@strlen.de designates 193.142.43.52 as permitted sender) smtp.mailfrom=fw@strlen.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663944852; a=rsa-sha256; cv=none; b=ZfDQwSc9D/mEp87wWsJWSPDO+WOzpGVL/+EGT/DODyYfi749/KhAzXcAPopMNsLWkTQ+j9 Bm0tppwCCFLh5CszO4MpnYKWiJIIQmnc7psBDkhuXqJfOtCnTKjeTxaCafmWO5Ilj6XE51 Fg+NTrTBxOE3nwMFtGUZyxREZSupLxY= Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf13.hostedemail.com: domain of fw@strlen.de designates 193.142.43.52 as permitted sender) smtp.mailfrom=fw@strlen.de X-Rspam-User: X-Stat-Signature: c8ygz3hrrwrg5i7juysdzknynfjkrqjs X-Rspamd-Queue-Id: E3F9320011 X-Rspamd-Server: rspam06 X-HE-Tag: 1663944851-607878 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: Uladzislau Rezki wrote: > On Fri, Sep 23, 2022 at 03:35:12PM +0200, Florian Westphal wrote: > > Michal Hocko wrote: > > > On Fri 23-09-22 12:38:58, Florian Westphal wrote: > > > > Martin Zaharinov reports BUG() in mm land for 5.19.10 kernel: > > > > kernel BUG at mm/vmalloc.c:2437! > > > > invalid opcode: 0000 [#1] SMP > > > > CPU: 28 PID: 0 Comm: swapper/28 Tainted: G W O 5.19.9 #1 > > > > [..] > > > > RIP: 0010:__get_vm_area_node+0x120/0x130 > > > > __vmalloc_node_range+0x96/0x1e0 > > > > kvmalloc_node+0x92/0xb0 > > > > bucket_table_alloc.isra.0+0x47/0x140 > > > > rhashtable_try_insert+0x3a4/0x440 > > > > rhashtable_insert_slow+0x1b/0x30 > > > > [..] > > > > > > > > bucket_table_alloc uses kvzallocGPF_ATOMIC). If kmalloc fails, this now > > > > falls through to vmalloc and hits code paths that assume GFP_KERNEL. > > > > > > > > Revert the problematic change and stay with slab allocator. > > > > > > Why don't you simply fix the caller? > > > > Uh, not following? > > > > kvzalloc(GFP_ATOMIC) was perfectly fine, is this illegal again? > > > > static struct vm_struct *__get_vm_area_node(unsigned long size, > unsigned long align, unsigned long shift, unsigned long flags, > unsigned long start, unsigned long end, int node, > gfp_t gfp_mask, const void *caller) > { > struct vmap_area *va; > struct vm_struct *area; > unsigned long requested_size = size; > > BUG_ON(in_interrupt()); > ... > > > vmalloc is not supposed to be called from the IRQ context. It uses kvzalloc, not vmalloc api. Before 2018, rhashtable did use kzalloc OR kvzalloc, depending on gfp_t. Quote from 93f976b5190df327939 changelog: As of ce91f6ee5b3b ("mm: kvmalloc does not fallback to vmalloc for incompatible gfp flags") we can simplify the caller and trust kvzalloc() to just do the right thing. I fear that if this isn't allowed it will result in hard-to-spot bugs because things will work fine until a fallback to vmalloc happens. rhashtable may not be the only user of kvmalloc api that rely on ability to call it from (soft)irq.