Date: Wed, 10 Sep 2003 01:29:28 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Eno Thereska <eno@andrew.cmu.edu> Cc: freebsd-fs@freebsd.org Subject: Re: free block bitmap Message-ID: <3F5EE0E8.40BF5801@mindspring.com> References: <3F5D0663.7020902@andrew.cmu.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
Eno Thereska wrote: > I am using FreeBSD4.4 with FFS as the underlying file system. > I need to examine which blocks in the file system > are currently in use. These blocks can be metadata or data blocks. > > I have looked at the FFS code and it seems the only way to get > the list of free blocks (or busy blocks) is by querying > each cylinder group's (cg) bitmap of free blocks. > > Is there a global bitmap that keeps track of busy/free blocks > over the entire file system or is the only option > the cg-by-cg lookup? You can do it two ways: 1) Iterate over every file in the filesystem, and examine their direct and indirect blocks. 2) Use the CG bitmaps. Out of curiosity, why aren't the CG bitmaps global enough for you? Is your problem that they are logically rather than physically contiguous? -- Terry
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3F5EE0E8.40BF5801>