Re: [PATCH] io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

On 11/11/25 11:15, Caleb Sander Mateos wrote:
> io_buffer_register_bvec() currently uses blk_rq_nr_phys_segments() as
> the number of bvecs in the request. However, bvecs may be split into
> multiple segments depending on the queue limits. Thus, the number of
> segments may overestimate the number of bvecs. For ublk devices, the
> only current users of io_buffer_register_bvec(), virt_boundary_mask,
> seg_boundary_mask, max_segments, and max_segment_size can all be set
> arbitrarily by the ublk server process.
> Set imu->nr_bvecs based on the number of bvecs the rq_for_each_bvec()
> loop actually yields. However, continue using blk_rq_nr_phys_segments()
> as an upper bound on the number of bvecs when allocating imu to avoid
> needing to iterate the bvecs a second time.
>
> Signed-off-by: Caleb Sander Mateos<csander@purestorage.com>
> Fixes: 27cb27b6d5ea ("io_uring: add support for kernel registered bvecs")


Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck