On 2021/9/20 20:41, David Sterba wrote:

On Mon, Sep 20, 2021 at 06:33:14PM +0800, Qu Wenruo wrote:

quoted

On 2021/9/17 20:49, Nikolay Borisov wrote:

quoted

On 17.09.21 г. 15:43, David Sterba wrote:

quoted

So should we add another helper that takes the exact number and drop the
parameter everwhere is 0 so it's just btrfs_io_bio_alloc() with the
fallback?

But by adding another helper we just introduce more indirection.

Actually I'd argue that if 0 is a sane default then BIO_MAX_VECS cannot
be any worse because:

a) It's a number which is as good as 0
b) It's even named. So this is technically better than a plain 0

Any final call on this?

I hope this could be an example for future optional parameters.

We have some existing codes using two different inline functions, and
both of them call a internal but exported function with "__" prefix.

We also have call sites passing all needed parameters just like Nikolay
suggested.

I'm fine with explicitly using BIO_MAX_VECS instead of 0. I'll update it
in the patch, no need to resend.

Thank you very much.

I'll no longer use this tricky way any more.

Thanks,
Qu