On 06/28/18 17:04, Kent Overstreet wrote:

On Thu, Jun 28, 2018 at 04:54:44PM -0700, Bart Van Assche wrote:

quoted

Thanks for chiming in. The linux-block mailing list is archived by multiple
websites. The entire e-mail thread is available on e.g.
https://www.mail-archive.com/linux-block@vger.kernel.org/msg23006.html.

I have a question for you: at least in kernel v4.17 bio_clone_bioset()
copies bi_vcnt from the source to the destination bio. However,
__bio_clone_fast() doesn't copy bi_vcnt. Isn't that an inconsistency?

No - when you use bio_clone_bioset() you get a bio that you own and can do
whatever you want with, so it does make sense for it to initialize bi_vcnt.

e.g. you could use bio_clone_bioset() when you're going to be bouncing a bio,
iterating over each bvec and allocating a new page and copying data from the old
page to the new page.

Hello Kent,

Have you considered to explain this in a comment above 
__bio_clone_fast() to avoid that the next person who reads that function 
gets confused?

Bart.