[PATCH RFC v3 01/22] blk-mq: Don't get budget for reserved requests

John Garry
2022-10-25T09:48:11Z

It should be possible to send reserved requests even when there is no
budget, so don't request a budget in that case.

This comes into play when we need to allocate a reserved request from the
target device request queue for error handling for that same device.

Signed-off-by: John Garry <john.garry@huawei.com>
---
block/blk-mq.c | 4 +++-
drivers/scsi/scsi_lib.c | 3 ++-
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 260adeb2e455..d8baabb32ea4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1955,11 +1955,13 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
errors = queued = 0;
do {
struct blk_mq_queue_data bd;
+ bool need_budget;

rq = list_first_entry(list, struct request, queuelist);

WARN_ON_ONCE(hctx != rq->mq_hctx);
- prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
+ need_budget = !nr_budgets && !blk_mq_is_reserved_rq(rq);
+ prep = blk_mq_prep_dispatch_rq(rq, need_budget);
if (prep != PREP_DISPATCH_OK)
break;

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index fa96d3cfdfa3..39d4fd124375 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -298,7 +298,8 @@ void scsi_device_unbusy(struct scsi_device *sdev, struct scsi_cmnd *cmd)
if (starget->can_queue > 0)
atomic_dec(&starget->target_busy);

- sbitmap_put(&sdev->budget_map, cmd->budget_token);
+ if (!blk_mq_is_reserved_rq(scsi_cmd_to_rq(cmd)))
+ sbitmap_put(&sdev->budget_map, cmd->budget_token);
cmd->budget_token = -1;
}

--
2.35.3