From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753533AbaBTWXY (ORCPT ); Thu, 20 Feb 2014 17:23:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58123 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751796AbaBTWXX (ORCPT ); Thu, 20 Feb 2014 17:23:23 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20140220211612.506074a7fd876e47130a8c5c@skynet.be> References: <20140220211612.506074a7fd876e47130a8c5c@skynet.be> To: Fabian Frederick Cc: dhowells@redhat.com, linux-kernel@vger.kernel.org, akpm , cl@linux-foundation.org Subject: Has slab ctor operation changed? -- was [PATCH 1/1] afs: afs_alloc_inode: use kmem_cache_zalloc Date: Thu, 20 Feb 2014 22:23:15 +0000 Message-ID: <32740.1392934995@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fabian Frederick wrote: > afs_vnode is currently cleared with 2 memsets after allocation and > 1 in constructor (afs_i_init_once). > -This patch calls zalloc for explicit zero fill. Ummm... This patch isn't necessarily correct in the substantiative portions. Since afs_i_init_once() is called by the slab allocator during the course of kmem_cache_alloc(), how does kmem_cache_zalloc() interact with that? IIRC, it used to be that the ctor() function was called when the pages were allocated to the slab - and it wasn't called again, even if the object was allocated, deallocated and reallocated. This means that things like locks and lists don't need reinitialising after allocation. So afs_i_init_once() theoretically constructs the stuff that can be reused, and afs_alloc_inode() therefore has to clear the non-reusable state. Of course, it's possible that the slab allocator no longer works like this... David