[RFC PATCH 1/2] block: change rq_integrity_vec to respect the iterator

[Mikulas Patocka]

On Thu, 16 May 2024, Ming Lei wrote:

> On Wed, May 15, 2024 at 03:28:11PM +0200, Mikulas Patocka wrote:
> > If we allocate a bio that is larger than NVMe maximum request size, attach
> > integrity metadata to it and send it to the NVMe subsystem, the integrity
> > metadata will be corrupted.
> > 
> > Splitting the bio works correctly. The function bio_split will clone the
> > bio, trim the iterator of the first bio and advance the iterator of the
> > second bio.
> > 
> > However, the function rq_integrity_vec has a bug - it returns the first
> > vector of the bio's metadata and completely disregards the metadata
> > iterator that was advanced when the bio was split. Thus, the second bio
> > uses the same metadata as the first bio and this leads to metadata
> > corruption.
> 
> Wrt. NVMe, inside blk_mq_submit_bio(), bio_integrity_prep() is called after
> bio is split, ->bi_integrity is actually allocated for every split bio, so I
> am not sure if the issue is related with bio splitting. Or is it related
> with DM over NVMe?

I created a dm-crypt patch that stores autenticated data in the bio 
integrity field: 
https://patchwork.kernel.org/project/linux-block/patch/703ffbcf-2fa8-56aa-2219-10254af26ba5@redhat.com/

And that patch needs this bugfix.

Mikulas

> However, rq_integrity_vec() may not work correctly in case of bio merge.
> 
> 
> Thanks, 
> Ming
>