From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id A946C4403D8 for ; Fri, 5 Feb 2016 11:11:38 -0500 (EST) Received: by mail-pa0-f47.google.com with SMTP id uo6so36823262pac.1 for ; Fri, 05 Feb 2016 08:11:38 -0800 (PST) Received: from mx2.parallels.com (mx2.parallels.com. [199.115.105.18]) by mx.google.com with ESMTPS id e64si24760376pfd.66.2016.02.05.08.11.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 05 Feb 2016 08:11:37 -0800 (PST) Date: Fri, 5 Feb 2016 19:11:24 +0300 From: Vladimir Davydov Subject: Re: [PATCHv6] mm: slab: free kmem_cache_node after destroy sysfs file Message-ID: <20160205161124.GA26693@esperanza> References: <1454687136-19298-1-git-send-email-dsafonov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1454687136-19298-1-git-send-email-dsafonov@virtuozzo.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dmitry Safonov Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 0x7f454c46@gmail.com, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim On Fri, Feb 05, 2016 at 06:45:36PM +0300, Dmitry Safonov wrote: > With enabled slub_debug alloc_calls_show will try to track location and > user of slab object on each online node, kmem_cache_node structure > shouldn't be freed till there is the last reference to sysfs file. > > Fixes the following panic: > [43963.463055] BUG: unable to handle kernel > [43963.463090] NULL pointer dereference at 0000000000000020 > [43963.463146] IP: [] list_locations+0x169/0x4e0 > [43963.463185] PGD 257304067 PUD 438456067 PMD 0 > [43963.463220] Oops: 0000 [#1] SMP > [43963.463850] CPU: 3 PID: 973074 Comm: cat ve: 0 Not tainted 3.10.0-229.7.2.ovz.9.30-00007-japdoll-dirty #2 9.30 > [43963.463913] Hardware name: DEPO Computers To Be Filled By O.E.M./H67DE3, BIOS L1.60c 07/14/2011 > [43963.463976] task: ffff88042a5dc5b0 ti: ffff88037f8d8000 task.ti: ffff88037f8d8000 > [43963.464036] RIP: 0010:[] [] list_locations+0x169/0x4e0 > [43963.464725] Call Trace: > [43963.464756] [] alloc_calls_show+0x1d/0x30 > [43963.464793] [] slab_attr_show+0x1b/0x30 > [43963.464829] [] sysfs_read_file+0x9a/0x1a0 > [43963.464865] [] vfs_read+0x9c/0x170 > [43963.464900] [] SyS_read+0x58/0xb0 > [43963.464936] [] system_call_fastpath+0x16/0x1b > [43963.464970] Code: 5e 07 12 00 b9 00 04 00 00 3d 00 04 00 00 0f 4f c1 3d 00 04 00 00 89 45 b0 0f 84 c3 00 00 00 48 63 45 b0 49 8b 9c c4 f8 00 00 00 <48> 8b 43 20 48 85 c0 74 b6 48 89 df e8 46 37 44 00 48 8b 53 10 > [43963.465119] RIP [] list_locations+0x169/0x4e0 > [43963.465155] RSP > [43963.465185] CR2: 0000000000000020 > > Separated nodes structures freeing into __kmem_cache_free_nodes and use > it at kmem_cache_release. Well, that's better indeed, although still not perfect. ... > diff --git a/mm/slab.c b/mm/slab.c > index 6ecc697..3ccdf3c 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -2276,6 +2276,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) > err = setup_cpu_cache(cachep, gfp); > if (err) { > __kmem_cache_shutdown(cachep); > + __kmem_cache_free_nodes(cachep); You don't need to call the whole shutdown procedure here - the cache hasn't been used yet. __kmem_cache_release (about it below) would be enough. > return err; > } > > @@ -2414,8 +2415,6 @@ int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate) > > int __kmem_cache_shutdown(struct kmem_cache *cachep) > { > - int i; > - struct kmem_cache_node *n; > int rc = __kmem_cache_shrink(cachep, false); > > if (rc) > @@ -2423,6 +2422,14 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep) > > free_percpu(cachep->cpu_cache); And how come ->cpu_cache (and ->cpu_slab in case of SLUB) is special? Can't sysfs access it either? I propose to introduce a method called __kmem_cache_release (instead of __kmem_cache_free_nodes), which would do all freeing, both per-cpu and per-node. Thanks, Vladimir > > + return 0; > +} > + > +void __kmem_cache_free_nodes(struct kmem_cache *cachep) > +{ > + int i; > + struct kmem_cache_node *n; > + > /* NUMA: free the node structures */ > for_each_kmem_cache_node(cachep, i, n) { > kfree(n->shared); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org