From mboxrd@z Thu Jan 1 00:00:00 1970 From: Coly Li Date: Tue, 01 Dec 2009 16:22:39 +0800 Subject: [Ocfs2-devel] what is global bitmap, block group, suballocator, etc In-Reply-To: <4B0CE3F2.8040503@oracle.com> References: <4B0CE011.3030403@suse.de> <4B0CE3F2.8040503@oracle.com> Message-ID: <4B14D24F.5090604@suse.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Hi Tao, Thanks for your reply. I spent some time to read the code and understand :) On 2009?11?25? 15:59, Tao Ma Wrote: > Hi Coly, > > Coly Li wrote: >> Hi list, >> >> There are some ocfs2 terminologies that I don't understand very well. >> After checking the ocfs2 wiki and kernel/tools >> code, I am still not sure whether I understand them correctly. >> >> - Global bitmap >> What's the usage of global bitmap? Which kind of resource allocation >> will set global bitmap? > global bitmap is a system file which indicates the usage of clusters in > the whole volume. It is a chain file. So it has a ocfs2_chain_list in > its ocfs2_dinode.id2. And the chain_list is a chain of many groups. A > group is a range of clusters and the 1st block of a group has a bitmap > to indicate which cluster(or block, cpg is used here) is allocated or not. What is a chain file ? Is it a file not for regular file data storage (a.k.a dinode->i_size == 0), but to record allocation chains of an ocfs2 volume (a.k.a dinode->id2.i_chain) ? Another question is, for each node (slot), should it have only 1 chain file ? If yes, I guess the chain number limit is ocfs2_chain_recs_per_inode(). -- Coly Li SuSE Labs