Re: [dm-devel] introduce dm-snap-mv

[Christoph Hellwig <hch lst de>]

On Fri, Oct 08, 2010 at 05:14:27PM +0800, McPacino wrote:
> Hi Christoph,
> 
> I have to take care the cache problem If using the bio directly.
> BHs can be released by kernel when necessary.
> 
> Is there any existing code using bio to read/write metadata
> blocks? How do they handle the timing freeing bios? I really
> wish to learn something form it.

If you actually need caching just use the pagecache, e.g.
read_mapping_page to read in your data.  That completely abstracts
away the underlying block size.