From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 9B4946B0087 for ; Thu, 18 Nov 2010 16:36:18 -0500 (EST) Received: from kpbe20.cbf.corp.google.com (kpbe20.cbf.corp.google.com [172.25.105.84]) by smtp-out.google.com with ESMTP id oAILaDJ0022793 for ; Thu, 18 Nov 2010 13:36:13 -0800 Received: from yxd5 (yxd5.prod.google.com [10.190.1.197]) by kpbe20.cbf.corp.google.com with ESMTP id oAILaAYt020370 for ; Thu, 18 Nov 2010 13:36:12 -0800 Received: by yxd5 with SMTP id 5so2367471yxd.20 for ; Thu, 18 Nov 2010 13:36:12 -0800 (PST) Date: Thu, 18 Nov 2010 13:36:08 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] slub: operate cache name memory same to slab and slob In-Reply-To: <1290114908.26343.721.camel@calx> Message-ID: References: <1290049259-20108-1-git-send-email-b32542@freescale.com> <1290114908.26343.721.camel@calx> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Matt Mackall Cc: b32542@freescale.com, linux-mm@kvack.org, cl@linux-foundation.org, penberg@cs.helsinki.fi, tytso@mit.edu, linux-kernel@vger.kernel.org, Zeng Zhaoming List-ID: On Thu, 18 Nov 2010, Matt Mackall wrote: > > Get a memory leak complaint about ext4: > > comm "mount", pid 1159, jiffies 4294904647 (age 6077.804s) > > hex dump (first 32 bytes): > > 65 78 74 34 5f 67 72 6f 75 70 69 6e 66 6f 5f 31 ext4_groupinfo_1 > > 30 00 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 0.kkkkkkkkkkkkk. > > backtrace: > > [] kmemleak_alloc+0x93/0xd0 > > [] __kmalloc_track_caller+0x30c/0x380 > > [] kstrdup+0x33/0x60 > > [] ext4_mb_init+0x4e0/0x550 > > [] ext4_fill_super+0x1e6e/0x2f60 > > [] mount_bdev+0x1c0/0x1f0 > > [] ext4_mount+0x1f/0x30 > > [] vfs_kern_mount+0x78/0x250 > > [] do_kern_mount+0x3e/0x100 > > [] do_mount+0x2e2/0x780 > > [] sys_mount+0xa4/0xd0 > > [] sysenter_do_call+0x12/0x38 > > [] 0xffffffff > > > > It is cause by slub manage the cache name different from slab and slob. > > In slab and slob, only reference to name, alloc and reclaim the memory > > is the duty of the code that invoked kmem_cache_create(). > > > > In slub, cache name duplicated when create. This ambiguity will cause > > some memory leaks and double free if kmem_cache_create() pass a > > dynamic malloc cache name. > > I don't get it. > > Caller allocates X, passes X to slub, slub duplicates X as X', and > properly frees X', then caller frees X. Yes, that's silly, but where's > the leak? > The leak in ext4_mb_init() above is because it is using kstrdup() to allocate the string itself and then on destroy uses kmem_cache_name() to attain the slub allocator's pointer to the name, not the memory the ext4 layer allocated itself. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org