[Ocfs2-tools-devel] [PATCH 10/20] bitmap: Add 2 fields to facilitate discontiguous block group.

[Joel Becker]

On Fri, Jun 11, 2010 at 07:57:54AM +0800, Tao Ma wrote:
> Joel Becker wrote:
> > 	Why are you creating multiple regions?  A region is a bitmap
> > hunk, not a disk hunk.  So you could just have one region with the
> > entire gd bitmap, but when you go to use it you could have specific
> > get/set functions that know how to read the right blkno.
> >   
> I was thinking of this, but have to give up finally. It is not easy to 
> integrate to our
> bitmap region code. ;)
> Say one gd has the following extent rec list [1000, 10], 
> [1100,10],[1200,10]...[2900,10].
> If we unit it to be a bitmap region we will have a [1000,200].
> But if we have a chance to have another gd has the following rec list 
> [1150,10]...
> we will have a [1150, 200]. This will collide with the original one. 
> Current bitmap region
> code can't handle this by now.

	How will it collide?  The 1000 is the address of the group
descriptor, and 200 is the number of blocks it describes.  It doesn't
have to be a physical count.
	What portion of the code hits this as a physical overlap?

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127