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

[McPacino <mcpacino gmail com>]

On Fri, Oct 8, 2010 at 5:24 PM, Christoph Hellwig <hch lst de> wrote:
> 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.

Hi Christoph,

My understanding is that, read_mapping_page_async() works in submit-wait
way. But whatI want is some function works in submit-callback way, just like
sumbit_bh(). Is there something like it in kernel?

thanks.
cong meng.

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