Doubt regarding BIO handling

[Prasad Joshi]

On Mon, Dec 27, 2010 at 6:01 AM, Gaurav Mahajan
<gauravmahajan2007 at gmail.com> wrote:
> Hi all,
>
> I have a doubt regarding the handling of bios.
>
> Suppose I receive a bio at some layer, and I want to split it into
> multiple bios. There are layers below the one I am working on and the
> final I/O operations will be handled by those layers. So, basically ,
> after some processing, I want to hand over the bio to the lower layer.
> Now, if I have split the original bio into multiple bios and submitted
> all the newly formed bios, I shall receive each such bio in the
> bio->bio_end_io function.
>
> Here is it necessary to merge these bios so that the original bio can
> be formed or is it ok to just split the original bio, receive the
> requested data in multiple bios and leave it at that ?
>

IMHO, you still need to call bio->bio_end_io on the original BIO
structure. So instead of splitting the original BIO. I think, You
might want to keep the original BIO as it is. The smaller BIOs need to
point back to original BIO and once all of the smaller BIOs have been
serviced. You might want to call bio_end_io() on the original BIO.

Have a look if you can use bi_private field.

> Looking forward to some help.....
>
> Regards,
> Gaurav
>
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