From: Eric Sandeen Subject: Re: upcoming kerneloops.org item: get_page_from_freelist Date: Thu, 25 Jun 2009 17:11:25 -0500 Message-ID: <4A43F60D.2040801@redhat.com> References: <20090624150714.c7264768.akpm@linux-foundation.org> <20090625132544.GB9995@mit.edu> <20090625193806.GA6472@mit.edu> <20090625194423.GB6472@mit.edu> <20090625203743.GD6472@mit.edu> <20090625212628.GO3385@webber.adilger.int> <20090625220504.GG6472@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: Theodore Tso , Andreas Dilger , David Rientjes , Andrew Morton , Linus Torvalds Received: from mx2.redhat.com ([66.187.237.31]:60369 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751897AbZFYWMT (ORCPT ); Thu, 25 Jun 2009 18:12:19 -0400 In-Reply-To: <20090625220504.GG6472@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Theodore Tso wrote: > On Thu, Jun 25, 2009 at 11:26:28PM +0200, Andreas Dilger wrote: >> IIRC there was also a good reason for this in the past, related to >> the buffers being submitted to the block device layer, and if they >> were allocated from the slab cache with CONFIG_DEBUG_SLAB or something >> similar enabled the buffer would be misaligned and cause grief. > > So what does SLAB/SLUB/SLOB do if we create a slab cache which is a > power of two? Can one of the allocators still return misaligned > blocks of memory in some circumstances? > > - Ted ecryptfs used to do kmalloc(PAGE_CACHE_SIZE) & virt_to_page on that, and with SLUB + slub debug, that gave back non-aligned memory, causing eventual corruption ... -Eric