Hi,
在 2025/9/9 20:18, Nilay Shroff 写道:
On 9/8/25 11:45 AM, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>
No functional changes are intended, make code cleaner and prepare to fix
the grow case in following patches.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/blk-mq.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1ff6370f7314..82fa81036115 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4931,21 +4931,25 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
blk_mq_tag_update_sched_shared_tags(q);
else
blk_mq_tag_resize_shared_tags(set, nr);
- } else {
+ } else if (!q->elevator) {
queue_for_each_hw_ctx(q, hctx, i) {
if (!hctx->tags)
continue;
- /*
- * If we're using an MQ scheduler, just update the
- * scheduler queue depth. This is similar to what the
- * old code would do.
- */
- if (hctx->sched_tags)
- ret = blk_mq_tag_update_depth(hctx,
- &hctx->sched_tags, nr);
- else
- ret = blk_mq_tag_update_depth(hctx,
- &hctx->tags, nr);
+ sbitmap_queue_resize(&hctx->tags->bitmap_tags,
+ nr - hctx->tags->nr_reserved_tags);
+ }
+ } else if (nr <= q->elevator->et->nr_requests) {
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!hctx->sched_tags)
+ continue;
+ sbitmap_queue_resize(&hctx->sched_tags->bitmap_tags,
+ nr - hctx->sched_tags->nr_reserved_tags);
+ }
+ } else {
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!hctx->sched_tags)
+ continue;
+ blk_mq_tag_update_depth(hctx, &hctx->sched_tags, nr);
if (ret)
goto out;
}
The above code is good however can this be bit simplified?
It's a bit difficult to follow through all nesting and so
could it be simplified as below:
if (shared-tags) {
if (elevator)
// resize sched-shared-tags bitmap
else
// resize shared-tags bitmap
} else {
// non-shared tags
if (elevator) {
if (new-depth-is-less-than-the-current-depth)
// resize sched-tags bitmap
else
// handle sched tags grow
} else
// resize tags bitmap
}
AFAIK, if - else if chain should be better than nested if - else, right?
If you don't mind, I can add comments to each else if chain to make code cleaner:
if () {
/* shared tags */
...
} else if () {
/* non-shared tags and elevator is none */
...
} else if () {
/* non-shared tags and elevator is not none, nr_requests doesn't grow */
...
} else () {
/* non-shared tags and elevator is not none, nr_requests grow */
...
}
Thanks,
Kuai
Thanks,
--Nilay
