From: Alex Tomas Subject: Re: booked-page-flag.patch Date: Thu, 15 Feb 2007 17:03:45 +0300 Message-ID: References: <20070215004504.023a90f0.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Theodore Ts'o" , Alex Tomas , "linux-ext4@vger.kernel.org" To: Andrew Morton Return-path: Received: from [80.71.245.246] ([80.71.245.246]:55718 "EHLO nsold.rialcom.ru" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1161318AbXBOVLR (ORCPT ); Thu, 15 Feb 2007 16:11:17 -0500 In-Reply-To: <20070215004504.023a90f0.akpm@linux-foundation.org> (Andrew Morton's message of "Thu\, 15 Feb 2007 00\:45\:04 -0800") Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org >>>>> Andrew Morton (AM) writes: AM> Sorry, we're seriously, seriously, seriously short on flags in the page AM> struct and this patch is going to need one heck of a good case for it to be AM> acceptable. AM> Even then, we should put a lot of effort into finding some way of avoiding AM> adding that page flag. One option might be to add a new radix-tree tag, AM> and defining it as "for filesytem usage". Or use PG_checked (which should AM> be renamed to to PG_fs_misc) (if that doesn't conflict with ext4's existing AM> use of PG_checked). Or use !PageMappedToDisk()? there is a difference between being mapped and "booked". the latter means that page isn't allocated yet, but space is reserved (including metadata) and we're sure we'll be able to allocate space when the page is being flushed. AM> These patches seem to have a number of issues - we should get them properly AM> commented and properly changelogged then get them on the wire for decent AM> review before investing too much in them, please. I've been reworking the delayed allocation patch to move part of it into VFS. I'll try to comment things better this time. thanks, Alex