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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF7E8C433F5 for ; Mon, 13 Dec 2021 13:43:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237835AbhLMNnb (ORCPT ); Mon, 13 Dec 2021 08:43:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230314AbhLMNn3 (ORCPT ); Mon, 13 Dec 2021 08:43:29 -0500 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0291FC061574; Mon, 13 Dec 2021 05:43:29 -0800 (PST) Received: by mail-pf1-x435.google.com with SMTP id 8so14974639pfo.4; Mon, 13 Dec 2021 05:43:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=+J3ydLfhX23J+J777y07I1sRvhVRSNugp1dJU717hFI=; b=S1I8QihitM5wvI9tD6XzXlNydYqjNAAXPtl/VXl7NK9c8iI9NG15DdzchdF75oP6qj 6F84H4aDqOlbTMhwBVOlIidAKRUU2R4Jm8s7FErfer2aFgodqpEzwLrk6m61vke1UERT ioVbiN6UQQVnrJLjFJJWSNk4abRyTrzpZ3IDtjCcdnvOY10aM3bLFS8m//NHAq3yrzIA v2DP5PYK4KUrkRpqcHf0yGnBVY+x0emX046coW/2GI7S7ldsIxfGwpMdPM/9hxq5VBfq vTKetK6qo23lGda7hPKFnUyWLHr4roGx2qHi+5x+IAu+Esaf2xpBNtJFqs/kgLtEANmQ Qf3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=+J3ydLfhX23J+J777y07I1sRvhVRSNugp1dJU717hFI=; b=6/HghDs0LLsLCJwQW6zouK8QnaW0VyQqrNhYB9umw9NM5P3H3bOMVMPObrJ6PGZYsU OFUYgbnILCSfZmOEfZwiLqnranhFHBz65hi8mgYMEF9OB35oNMKi+sEeuz72AbYCBKwh +6aO3CnqkzywAm11leNmd0wESkAiyUnoqwkm5+FUX2FGrWoZm4opP9IZ/O0BFtXaeDuh Qs1FrQS0U33w3NW0b5IZZ8IJ/jTnI3LpkewGHT1UmKi2CmWKFr8O3ts5njtAiYVpHpYH QgxBDM8HwphmruDJhFSTt6MJhpnIIYDH2eqBAkphIuR/2pNTll3lKRy5momZJ1dkG45i Ul1Q== X-Gm-Message-State: AOAM530msm/i8po2/tzo5y6nuR5cuLugZWebt7x16b1woDzsgPzHeWP0 7sWXxoSl6z95z3rw4dE6slM= X-Google-Smtp-Source: ABdhPJxrK8CSXwJ9wJcqa131184oXUIWwfLmqn2EON2QuG7DBdvI31pZFgWPEQAEO6i1D0/GFedfsw== X-Received: by 2002:a63:5a18:: with SMTP id o24mr52037322pgb.459.1639403008517; Mon, 13 Dec 2021 05:43:28 -0800 (PST) Received: from odroid ([114.29.23.242]) by smtp.gmail.com with ESMTPSA id x1sm10226500pgh.1.2021.12.13.05.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Dec 2021 05:43:28 -0800 (PST) Date: Mon, 13 Dec 2021 13:43:19 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, cl@linux.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org, stable@vger.kernel.org, Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka Subject: Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone Message-ID: <20211213134319.GA997240@odroid> References: <20211213122712.23805-1-bhe@redhat.com> <20211213122712.23805-6-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211213122712.23805-6-bhe@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Baoquan. I have a question on your code. On Mon, Dec 13, 2021 at 08:27:12PM +0800, Baoquan He wrote: > Dma-kmalloc will be created as long as CONFIG_ZONE_DMA is enabled. > However, it will fail if DMA zone has no managed pages. The failure > can be seen in kdump kernel of x86_64 as below: > > CPU: 0 PID: 65 Comm: kworker/u2:1 Not tainted 5.14.0-rc2+ #9 > Hardware name: Intel Corporation SandyBridge Platform/To be filled by O.E.M., BIOS RMLSDP.86I.R2.28.D690.1306271008 06/27/2013 > Workqueue: events_unbound async_run_entry_fn > Call Trace: > dump_stack_lvl+0x57/0x72 > warn_alloc.cold+0x72/0xd6 > __alloc_pages_slowpath.constprop.0+0xf56/0xf70 > __alloc_pages+0x23b/0x2b0 > allocate_slab+0x406/0x630 > ___slab_alloc+0x4b1/0x7e0 > ? sr_probe+0x200/0x600 > ? lock_acquire+0xc4/0x2e0 > ? fs_reclaim_acquire+0x4d/0xe0 > ? lock_is_held_type+0xa7/0x120 > ? sr_probe+0x200/0x600 > ? __slab_alloc+0x67/0x90 > __slab_alloc+0x67/0x90 > ? sr_probe+0x200/0x600 > ? sr_probe+0x200/0x600 > kmem_cache_alloc_trace+0x259/0x270 > sr_probe+0x200/0x600 > ...... > bus_probe_device+0x9f/0xb0 > device_add+0x3d2/0x970 > ...... > __scsi_add_device+0xea/0x100 > ata_scsi_scan_host+0x97/0x1d0 > async_run_entry_fn+0x30/0x130 > process_one_work+0x2b0/0x5c0 > worker_thread+0x55/0x3c0 > ? process_one_work+0x5c0/0x5c0 > kthread+0x149/0x170 > ? set_kthread_struct+0x40/0x40 > ret_from_fork+0x22/0x30 > Mem-Info: > ...... > > The above failure happened when calling kmalloc() to allocate buffer with > GFP_DMA. It requests to allocate slab page from DMA zone while no managed > pages in there. > sr_probe() > --> get_capabilities() > --> buffer = kmalloc(512, GFP_KERNEL | GFP_DMA); > > The DMA zone should be checked if it has managed pages, then try to create > dma-kmalloc. > What is problem here? The slab allocator requested buddy allocator with GFP_DMA, and then buddy allocator failed to allocate page in DMA zone because there was no page in DMA zone. and then the buddy allocator called warn_alloc because it failed at allocating page. Looking at warn, I don't understand what the problem is. > --- > mm/slab_common.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index e5d080a93009..ae4ef0f8903a 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -878,6 +878,9 @@ void __init create_kmalloc_caches(slab_flags_t flags) > { > int i; > enum kmalloc_cache_type type; > +#ifdef CONFIG_ZONE_DMA > + bool managed_dma; > +#endif > > /* > * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined > @@ -905,10 +908,16 @@ void __init create_kmalloc_caches(slab_flags_t flags) > slab_state = UP; > > #ifdef CONFIG_ZONE_DMA > + managed_dma = has_managed_dma(); > + > for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) { > struct kmem_cache *s = kmalloc_caches[KMALLOC_NORMAL][i]; > > if (s) { > + if (!managed_dma) { > + kmalloc_caches[KMALLOC_DMA][i] = kmalloc_caches[KMALLOC_NORMAL][i]; > + continue; > + } This code is copying normal kmalloc caches to DMA kmalloc caches. With this code, the kmalloc() with GFP_DMA will succeed even if allocated memory is not actually from DMA zone. Is that really what you want? Maybe the function get_capabilities() want to allocate memory even if it's not from DMA zone, but other callers will not expect that. Thanks, Hyeonggon. > kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache( > kmalloc_info[i].name[KMALLOC_DMA], > kmalloc_info[i].size, > -- > 2.17.2 > >