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authorJens Axboe <axboe@kernel.dk>2022-09-21 08:22:09 -0600
committerJens Axboe <axboe@kernel.dk>2022-09-30 07:48:00 -0600
commit4b6a5d9cea911424e84107df8c4eb8317938d2cd (patch)
treee62e8091470a63c018855e263bd10be2ee353c67 /block
parente73a625bc24880f1fe5abaa89bb63e0918fbd66c (diff)
downloadlwn-4b6a5d9cea911424e84107df8c4eb8317938d2cd.tar.gz
lwn-4b6a5d9cea911424e84107df8c4eb8317938d2cd.zip
block: enable batched allocation for blk_mq_alloc_request()
The filesystem IO path can take advantage of allocating batches of requests, if the underlying submitter tells the block layer about it through the blk_plug. For passthrough IO, the exported API is the blk_mq_alloc_request() helper, and that one does not allow for request caching. Wire up request caching for blk_mq_alloc_request(), which is generally done without having a bio available upfront. Tested-by: Anuj Gupta <anuj20.g@samsung.com> Reviewed-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c80
1 files changed, 71 insertions, 9 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 83492d942348..b32f70f38c6e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -510,25 +510,87 @@ retry:
alloc_time_ns);
}
-struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
- blk_mq_req_flags_t flags)
+static struct request *blk_mq_rq_cache_fill(struct request_queue *q,
+ struct blk_plug *plug,
+ blk_opf_t opf,
+ blk_mq_req_flags_t flags)
{
struct blk_mq_alloc_data data = {
.q = q,
.flags = flags,
.cmd_flags = opf,
- .nr_tags = 1,
+ .nr_tags = plug->nr_ios,
+ .cached_rq = &plug->cached_rq,
};
struct request *rq;
- int ret;
- ret = blk_queue_enter(q, flags);
- if (ret)
- return ERR_PTR(ret);
+ if (blk_queue_enter(q, flags))
+ return NULL;
+
+ plug->nr_ios = 1;
rq = __blk_mq_alloc_requests(&data);
- if (!rq)
- goto out_queue_exit;
+ if (unlikely(!rq))
+ blk_queue_exit(q);
+ return rq;
+}
+
+static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
+ blk_opf_t opf,
+ blk_mq_req_flags_t flags)
+{
+ struct blk_plug *plug = current->plug;
+ struct request *rq;
+
+ if (!plug)
+ return NULL;
+ if (rq_list_empty(plug->cached_rq)) {
+ if (plug->nr_ios == 1)
+ return NULL;
+ rq = blk_mq_rq_cache_fill(q, plug, opf, flags);
+ if (rq)
+ goto got_it;
+ return NULL;
+ }
+ rq = rq_list_peek(&plug->cached_rq);
+ if (!rq || rq->q != q)
+ return NULL;
+
+ if (blk_mq_get_hctx_type(opf) != rq->mq_hctx->type)
+ return NULL;
+ if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
+ return NULL;
+
+ plug->cached_rq = rq_list_next(rq);
+got_it:
+ rq->cmd_flags = opf;
+ INIT_LIST_HEAD(&rq->queuelist);
+ return rq;
+}
+
+struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
+ blk_mq_req_flags_t flags)
+{
+ struct request *rq;
+
+ rq = blk_mq_alloc_cached_request(q, opf, flags);
+ if (!rq) {
+ struct blk_mq_alloc_data data = {
+ .q = q,
+ .flags = flags,
+ .cmd_flags = opf,
+ .nr_tags = 1,
+ };
+ int ret;
+
+ ret = blk_queue_enter(q, flags);
+ if (ret)
+ return ERR_PTR(ret);
+
+ rq = __blk_mq_alloc_requests(&data);
+ if (!rq)
+ goto out_queue_exit;
+ }
rq->__data_len = 0;
rq->__sector = (sector_t) -1;
rq->bio = rq->biotail = NULL;