From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161326AbcE3NJG (ORCPT ); Mon, 30 May 2016 09:09:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:40976 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161204AbcE3NJE (ORCPT ); Mon, 30 May 2016 09:09:04 -0400 Date: Mon, 30 May 2016 15:09:01 +0200 From: Jan Kara To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, LKML , Michal Hocko , "Theodore Ts'o" , Jan Kara Subject: Re: [PATCH 17/17] jbd2: get rid of superfluous __GFP_REPEAT Message-ID: <20160530130901.GE3690@quack2.suse.cz> References: <1464599699-30131-1-git-send-email-mhocko@kernel.org> <1464599699-30131-18-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464599699-30131-18-git-send-email-mhocko@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 30-05-16 11:14:59, Michal Hocko wrote: > From: Michal Hocko > > jbd2_alloc is explicit about its allocation preferences wrt. the > allocation size. Sub page allocations go to the slab allocator > and larger are using either the page allocator or vmalloc. This > is all good but the logic is unnecessarily complex. > 1) as per Ted, the vmalloc fallback is a left-over: > : jbd2_alloc is only passed in the bh->b_size, which can't be > > : PAGE_SIZE, so the code path that calls vmalloc() should never get > : called. When we conveted jbd2_alloc() to suppor sub-page size > : allocations in commit d2eecb039368, there was an assumption that it > : could be called with a size greater than PAGE_SIZE, but that's > : certaily not true today. > Moreover vmalloc allocation might even lead to a deadlock because > the callers expect GFP_NOFS context while vmalloc is GFP_KERNEL. > > 2) __GFP_REPEAT for requests <= PAGE_ALLOC_COSTLY_ORDER is ignored > since the flag was introduced. > > Let's simplify the code flow and use the slab allocator for sub-page > requests and the page allocator for others. Even though order > 0 is > not currently used as per above leave that option open. > > Cc: "Theodore Ts'o" > Cc: Jan Kara > Signed-off-by: Michal Hocko The patch looks good. You can add: Reviewed-by: Jan Kara Since the patch is in pretty stable parts of JBD2 I think it is fine to merge it through Andrew's tree with the rest of the series. Honza -- Jan Kara SUSE Labs, CR