Re: [PATCH v1 06/11] io_uring/kbuf: add buffer ring pinning/unpinning

[Caleb Sander Mateos <csander@purestorage.com>]

On Mon, Feb 9, 2026 at 5:07 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 2/9/26 5:28 PM, Joanne Koong wrote:
> > +int io_uring_buf_ring_pin(struct io_uring_cmd *cmd, unsigned buf_group,
> > +                       unsigned issue_flags, struct io_buffer_list **bl)
> > +{
> > +     struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
> > +     struct io_buffer_list *buffer_list;
> > +     int ret = -EINVAL;
>
> Probably use the usual struct io_buffer_list *bl here and either use an
> ERR_PTR return, or rename the passed on **bl to **blret or something.
>
> > +int io_uring_buf_ring_unpin(struct io_uring_cmd *cmd, unsigned buf_group,
> > +                    unsigned issue_flags)
> > +{
> > +     struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
> > +     struct io_buffer_list *bl;
> > +     int ret = -EINVAL;
> > +
> > +     io_ring_submit_lock(ctx, issue_flags);
> > +
> > +     bl = io_buffer_get_list(ctx, buf_group);
> > +     if (bl && (bl->flags & IOBL_BUF_RING) && (bl->flags & IOBL_PINNED)) {
>
> Usually done as:
>
>         if ((bl->flags & (IOBL_BUF_RING|IOBL_PINNED)) == (IOBL_BUF_RING|IOBL_PINNED))

FWIW, modern compilers will perform this optimization automatically.
They'll even optimize it further to !(~bl->flags &
(IOBL_BUF_RING|IOBL_PINNED)): https://godbolt.org/z/xGoP4TfhP

Best,
Caleb

>
> and maybe then just have an earlier
>
>         if (!bl)
>                 goto err;
>
> > +             bl->flags &= ~IOBL_PINNED;
> > +             ret = 0;
> > +     }
> err:
> > +     io_ring_submit_unlock(ctx, issue_flags);
> > +     return ret;
> > +}
>
> to avoid making it way too long. For io_uring, it's fine to exceed 80
> chars where it makes sense.
>
> --
> Jens Axboe