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[95.193.99.240]) by smtp.gmail.com with ESMTPSA id y6-20020ac24466000000b00492e69be4d6sm1493029lfl.27.2022.09.23.08.10.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Sep 2022 08:10:05 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 23 Sep 2022 17:10:03 +0200 To: Florian Westphal Cc: Uladzislau Rezki , 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: References: <20220923103858.26729-1-fw@strlen.de> <20220923133512.GE22541@breakpoint.cc> <20220923145409.GF22541@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220923145409.GF22541@breakpoint.cc> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663945809; a=rsa-sha256; cv=none; b=PzgevkTuFCagjjgEfTgUCJaaRioboVBU8ZpwPJYUsN2CIkDNwyCVcAVXgxXtiDKinfYu4l 5n9TwaVjLsuTg/RvWV5z0tAyFzgXOXb38Sj030S0euvCoi+LX6dQd+BJjOtaLhmFNv+fYs EOD0TH176uRJiOFj/gWDuUi945mtfPU= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=BIAfiW5N; spf=pass (imf22.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.48 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663945809; 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=hwfpnky+kIGo+6BQx8KdkTZdwoBXJ3O3qQ3V/MMGJ2A=; b=fBZTb35RWUJZzCQricM4M8onf0D24oq3W9ZYHSqr27y9d2xHSYIywOZwBH/mL50VTZu99p KJUIHaON9DGGGzRutPMpFU9fs/meLdfa6QrhUz8RXlf/P3z4NhwbN7t2JaaVlOaXBDAknt VmTilZpoThDxTfUFuW0s0L8UrWuoC/M= Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=BIAfiW5N; spf=pass (imf22.hostedemail.com: domain of urezki@gmail.com designates 209.85.167.48 as permitted sender) smtp.mailfrom=urezki@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: ucxdbzp8ebyh7in9i18q78kgrgcmo7in X-Rspamd-Queue-Id: 47CC6C001F X-Rspamd-Server: rspam02 X-HE-Tag: 1663945809-597799 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 Fri, Sep 23, 2022 at 04:54:09PM +0200, Florian Westphal wrote: > 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. > Doing the "p = kmalloc(sizeof(*p), GFP_ATOMIC);" from an atomic context is also a problem nowadays. Such code should be fixed across the kernel because of PREEMPT_RT support. -- Uladzislau Rezki