Re: [dm-devel] [PATCH v2 09/14] block: Add an explicit bio flag for bios that own their bvec

[Kent Overstreet <koverstreet google com>]

On Thu, May 24, 2012 at 07:57:34PM +0300, Boaz Harrosh wrote:
> How do you insure that the original bio which owns the
> bvec is not freed before the split-out bio.
> 
> Perhaps calling code needs to make sure by taking an extra
> ref on the original bio, or something. If so a big fat comment
> at bio_split is do.

Yeah, just added that.

> 
> And I understand you did not like my suggestion of negating
> the meaning of the flag, so the default is zero?
> Please say why?

I liked it at first, but I think I prefer having the flag be set
if bio_free() must take some action; i.e. you set the flag when you
allocate bi_io_vec. Also, I think bio_alloc_bioset() getting
reimplemented is less likely than people open coding bio splitting or
something that shares bi_io_vec in the future, so it's slightlry less
likely to be used wrong this way.