[PATCH 1/4] block: provide helpers for rq_list manipulation

Jens Axboe
2021-10-13T16:49:43Z

Instead of open-coding the list additions, traversal, and removal,
provide a basic set of helpers.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/blk-mq.c | 21 +++++----------------
include/linux/blk-mq.h | 25 +++++++++++++++++++++++++
2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6dfd3aaa6073..46a91e5fabc5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -426,10 +426,10 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
tag = tag_offset + i;
tags &= ~(1UL << i);
rq = blk_mq_rq_ctx_init(data, tag, alloc_time_ns);
- rq->rq_next = *data->cached_rq;
- *data->cached_rq = rq;
+ rq_list_add_tail(data->cached_rq, rq);
}
data->nr_tags -= nr;
+ return rq_list_pop(data->cached_rq);
} else {
/*
* Waiting allocations only fail because of an inactive hctx.
@@ -453,14 +453,6 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)

return blk_mq_rq_ctx_init(data, tag, alloc_time_ns);
}
-
- if (data->cached_rq) {
- rq = *data->cached_rq;
- *data->cached_rq = rq->rq_next;
- return rq;
- }
-
- return NULL;
}

struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
@@ -603,11 +595,9 @@ EXPORT_SYMBOL_GPL(blk_mq_free_request);

void blk_mq_free_plug_rqs(struct blk_plug *plug)
{
- while (plug->cached_rq) {
- struct request *rq;
+ struct request *rq;

- rq = plug->cached_rq;
- plug->cached_rq = rq->rq_next;
+ while ((rq = rq_list_pop(&plug->cached_rq)) != NULL) {
percpu_ref_get(&rq->q->q_usage_counter);
blk_mq_free_request(rq);
}
@@ -2264,8 +2254,7 @@ void blk_mq_submit_bio(struct bio *bio)

plug = blk_mq_plug(q, bio);
if (plug && plug->cached_rq) {
- rq = plug->cached_rq;
- plug->cached_rq = rq->rq_next;
+ rq = rq_list_pop(&plug->cached_rq);
INIT_LIST_HEAD(&rq->queuelist);
} else {
struct blk_mq_alloc_data data = {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a9c1d0882550..c05560524841 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -473,6 +473,31 @@ struct blk_mq_tag_set {
struct list_head tag_list;
};

+#define rq_list_add_tail(listptr, rq) do { \
+ (rq)->rq_next = *(listptr); \
+ *(listptr) = rq; \
+} while (0)
+
+#define rq_list_pop(listptr) \
+({ \
+ struct request *__req = NULL; \
+ if ((listptr) && *(listptr)) { \
+ __req = *(listptr); \
+ *(listptr) = __req->rq_next; \
+ } \
+ __req; \
+})
+
+#define rq_list_peek(listptr) \
+({ \
+ struct request *__req = NULL; \
+ if ((listptr) && *(listptr)) \
+ __req = *(listptr); \
+ __req; \
+})
+
+#define rq_list_next(rq) (rq)->rq_next
+
/**
* struct blk_mq_queue_data - Data about a request inserted in a queue
*
--
2.33.0