From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 9A1466B0087 for ; Thu, 18 Nov 2010 16:41:21 -0500 (EST) Message-ID: <4CE59D84.4050501@cs.helsinki.fi> Date: Thu, 18 Nov 2010 23:41:24 +0200 From: Pekka Enberg MIME-Version: 1.0 Subject: Re: [PATCH] slub: operate cache name memory same to slab and slob References: <1290049259-20108-1-git-send-email-b32542@freescale.com> <1290114908.26343.721.camel@calx> In-Reply-To: <1290114908.26343.721.camel@calx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Matt Mackall Cc: b32542@freescale.com, linux-mm@kvack.org, cl@linux-foundation.org, tytso@mit.edu, linux-kernel@vger.kernel.org, Zeng Zhaoming List-ID: On 18.11.2010 23.15, Matt Mackall wrote: > On Thu, 2010-11-18 at 11:00 +0800, b32542@freescale.com wrote: >> From: Zeng Zhaoming >> >> 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? > > But slub and slab should obviously both manage names in the same way, > namely the historical "caller allocates" way. So: > > Acked-by: Matt Mackall The kstrdup() is there because of SLUB cache merging. See commit 84c1cf62465e2fb0a692620dcfeb52323ab03d48 ("SLUB: Fix merged slab cache names") for details. -- 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