On 11/6/24 5:26 AM, Ming Lei wrote:
> Prepare for supporting kernel buffer in case of io group, in which group
> leader leases kernel buffer to io_uring, and consumed by io_uring OPs.
>
> So reuse io_mapped_buf for group kernel buffer, and unfortunately
> io_import_fixed() can't be reused since userspace fixed buffer is
> virt-contiguous, but it isn't true for kernel buffer.
>
> Also kernel buffer lifetime is bound with group leader request, it isn't
> necessary to use rsrc_node for tracking its lifetime, especially it needs
> extra allocation of rsrc_node for each IO.
While it isn't strictly necessary, I do think it'd clean up the io_kiocb
parts and hopefully unify the assign and put path more. So I'd strongly
suggest you do use an io_rsrc_node, even if it does just map the
io_mapped_buf for this.
> +struct io_mapped_buf {
> + u64 start;
> + unsigned int len;
> + unsigned int nr_bvecs;
> +
> + /* kbuf hasn't refs and accounting, its lifetime is bound with req */
> + union {
> + struct {
> + refcount_t refs;
> + unsigned int acct_pages;
> + };
> + /* pbvec is only for kbuf */
> + const struct bio_vec *pbvec;
> + };
> + unsigned int folio_shift:6;
> + unsigned int dir:1; /* ITER_DEST or ITER_SOURCE */
> + unsigned int kbuf:1; /* kernel buffer or not */
> + /* offset in the 1st bvec, for kbuf only */
> + unsigned int offset;
> + struct bio_vec bvec[] __counted_by(nr_bvecs);
> +};
And then I'd get rid of this union, and have it follow the normal rules
for an io_mapped_buf in that the refs are valid. Yes it'll take 8b more,
but honestly I think unifying these bits and keeping it consistent is a
LOT more important than saving a bit of space.
This is imho the last piece missing to make this conform more nicely
with how resource nodes are generally handled and used.
--
Jens Axboe
