From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id CC7506B025F for ; Mon, 14 Aug 2017 17:29:36 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id l30so11673174pgc.15 for ; Mon, 14 Aug 2017 14:29:36 -0700 (PDT) Received: from mail-pg0-x22d.google.com (mail-pg0-x22d.google.com. [2607:f8b0:400e:c05::22d]) by mx.google.com with ESMTPS id t12si4675094pfi.3.2017.08.14.14.29.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Aug 2017 14:29:33 -0700 (PDT) Received: by mail-pg0-x22d.google.com with SMTP id y129so54898104pgy.4 for ; Mon, 14 Aug 2017 14:29:33 -0700 (PDT) Date: Mon, 14 Aug 2017 14:29:31 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH] slub: fix per memcg cache leak on css offline In-Reply-To: <20170812181134.25027-1-vdavydov.dev@gmail.com> Message-ID: References: <20170812181134.25027-1-vdavydov.dev@gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Andrew Morton , Michal Hocko , Johannes Weiner , Christoph Lameter , Pekka Enberg , Joonsoo Kim , Andrei Vagin , Tejun Heo , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Sat, 12 Aug 2017, Vladimir Davydov wrote: > To avoid a possible deadlock, sysfs_slab_remove() schedules an > asynchronous work to delete sysfs entries corresponding to the kmem > cache. To ensure the cache isn't freed before the work function is > called, it takes a reference to the cache kobject. The reference is > supposed to be released by the work function. However, the work function > (sysfs_slab_remove_workfn()) does nothing in case the cache sysfs entry > has already been deleted, leaking the kobject and the corresponding > cache. This may happen on a per memcg cache destruction, because sysfs > entries of a per memcg cache are deleted on memcg offline if the cache > is empty (see __kmemcg_cache_deactivate()). > > The kmemleak report looks like this: > > unreferenced object 0xffff9f798a79f540 (size 32): > comm "kworker/1:4", pid 15416, jiffies 4307432429 (age 28687.554s) > hex dump (first 32 bytes): > 6b 6d 61 6c 6c 6f 63 2d 31 36 28 31 35 39 39 3a kmalloc-16(1599: > 6e 65 77 72 6f 6f 74 29 00 23 6b c0 ff ff ff ff newroot).#k..... > backtrace: > [] kmemleak_alloc+0x4a/0xa0 > [] __kmalloc_track_caller+0x148/0x2c0 > [] kvasprintf+0x66/0xd0 > [] kasprintf+0x49/0x70 > [] memcg_create_kmem_cache+0xe6/0x160 > [] memcg_kmem_cache_create_func+0x20/0x110 > [] process_one_work+0x205/0x5d0 > [] worker_thread+0x4e/0x3a0 > [] kthread+0x109/0x140 > [] ret_from_fork+0x2a/0x40 > [] 0xffffffffffffffff > unreferenced object 0xffff9f79b6136840 (size 416): > comm "kworker/1:4", pid 15416, jiffies 4307432429 (age 28687.573s) > hex dump (first 32 bytes): > 40 fb 80 c2 3e 33 00 00 00 00 00 40 00 00 00 00 @...>3.....@.... > 00 00 00 00 00 00 00 00 10 00 00 00 10 00 00 00 ................ > backtrace: > [] kmemleak_alloc+0x4a/0xa0 > [] kmem_cache_alloc+0x128/0x280 > [] create_cache+0x3b/0x1e0 > [] memcg_create_kmem_cache+0x118/0x160 > [] memcg_kmem_cache_create_func+0x20/0x110 > [] process_one_work+0x205/0x5d0 > [] worker_thread+0x4e/0x3a0 > [] kthread+0x109/0x140 > [] ret_from_fork+0x2a/0x40 > [] 0xffffffffffffffff > > Fix the leak by adding the missing call to kobject_put() to > sysfs_slab_remove_workfn(). > > Signed-off-by: Vladimir Davydov > Reported-and-tested-by: Andrei Vagin > Acked-by: Tejun Heo > Cc: Michal Hocko > Cc: Johannes Weiner > Cc: Christoph Lameter > Cc: Pekka Enberg > Cc: David Rientjes > Cc: Joonsoo Kim > Fixes: 3b7b314053d02 ("slub: make sysfs file removal asynchronous") Acked-by: David Rientjes -- 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