On Tue, Mar 01, 2022 at 05:37:17AM -0800, Christoph Hellwig wrote:
> > - hctxs[i] = blk_mq_alloc_and_init_hctx(set, q, i,
> > - old_node);
> > - WARN_ON_ONCE(!hctxs[i]);
> > + WARN_ON_ONCE(!blk_mq_alloc_and_init_hctx(set, q, i,
> > + old_node));
>
>
> Please avoid doing the actual work inside a WARN_ON statement.
OK.
>
> >
> > for (; j < end; j++) {
> > - struct blk_mq_hw_ctx *hctx = hctxs[j];
> > + struct blk_mq_hw_ctx *hctx = blk_mq_get_hctx(q, j);
> >
> > - if (hctx) {
> > + if (hctx)
> > blk_mq_exit_hctx(q, set, hctx, j);
> > - hctxs[j] = NULL;
> > - }
> > }
>
> Instead of a for loop that does xa_loads repeatedly this can just
> use xa_for_each_range. Same for a bunch of other loops like that,
> e.g. in blk_mq_unregister_dev or the __blk_mq_register_dev failure
> path.
>
> > @@ -919,12 +919,12 @@ static inline void *blk_mq_rq_to_pdu(struct request *rq)
> > static inline struct blk_mq_hw_ctx *blk_mq_get_hctx(struct request_queue *q,
> > unsigned int hctx_idx)
> > {
> > - return q->queue_hw_ctx[hctx_idx];
> > + return xa_load(&q->hctx_table, hctx_idx);
> > }
> >
> > #define queue_for_each_hw_ctx(q, hctx, i) \
> > for ((i) = 0; (i) < (q)->nr_hw_queues && \
> > - ({ hctx = blk_mq_get_hctx((q), (i)); 1; }); (i)++)
> > + (hctx = blk_mq_get_hctx((q), (i))); (i)++)
>
> This should be using a xa_for_each loop.
I did considered xa_for_each(), but it requires rcu read lock.
Also queue_for_each_hw_ctx() is supposed to not run in fast path,
meantime xa_load() is lightweight enough too, so repeated xa_load()
is fine here.
Thanks,
Ming
