From: Theodore Tso Subject: Re: [PATCH -V2 4/5] ext4: Use both hi and lo bits of the group desc values. Date: Sun, 23 Nov 2008 20:21:13 -0500 Message-ID: <20081124012113.GA2163@mit.edu> References: <1227285875-18011-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1227285875-18011-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1227285875-18011-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1227285875-18011-4-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <4926F00D.6030403@redhat.com> <20081121174110.GH11212@skywalker> <4926F599.5040605@redhat.com> <20081123040939.GU3186@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , "Aneesh Kumar K.V" , Coly Li , cmm@us.ibm.com, linux-ext4@vger.kernel.org To: Andreas Dilger Return-path: Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:40694 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbYKXB03 (ORCPT ); Sun, 23 Nov 2008 20:26:29 -0500 Content-Disposition: inline In-Reply-To: <20081123040939.GU3186@webber.adilger.int> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sat, Nov 22, 2008 at 10:09:39PM -0600, Andreas Dilger wrote: > On Nov 21, 2008 11:53 -0600, Eric Sandeen wrote: > > Ok, and for the rest? (free_blocks, free_inodes) - I guess these are > > only needed for > 2^32 block filesystems? > > Actually, since this is a per-group number, I'm not sure why this is > needed at all. I don't object to keeping the helper functions though. For most systems, it wn't be needed at all. However, for filesystems with block sizes >= 8k, we run into a limit where the maximum number of blocks and inodes we can support per block group is 65528 (we can't support 65536 since that would cause bg_free_blocks_count and/or bg_free_blocks_count, which are both __u16 types, to overflow). So on systems with a page size > 4k, or if Christoph's patch to support fs block sizes > page size ever makes it into mainline, this support could be useful. - Ted