Re: [PATCH] scsi: ufs: core: quiesce request queues before check pending cmds

[Bart Van Assche <bvanassche@acm.org>]

On 6/7/24 3:06 AM, Ziqi Chen wrote:
> Fix this race condition by quiescing the request queues before calling
> ufshcd_pending_cmds() so that block layer won't touch the budget map
> when ufshcd_pending_cmds() is working on it. In addition, remove the
> scsi layer blocking/unblocking to reduce redundancies and latencies.

Can you please help with testing whether the patch below would be a good
alternative to your patch (compile-tested only)?

Thanks,

Bart.

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index aa00978c6c0e..1d981283b03c 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -332,14 +332,12 @@ static void ufshcd_configure_wb(struct ufs_hba *hba)

  static void ufshcd_scsi_unblock_requests(struct ufs_hba *hba)
  {
-	if (atomic_dec_and_test(&hba->scsi_block_reqs_cnt))
-		scsi_unblock_requests(hba->host);
+	blk_mq_quiesce_tagset(&hba->host->tag_set);
  }

  static void ufshcd_scsi_block_requests(struct ufs_hba *hba)
  {
-	if (atomic_inc_return(&hba->scsi_block_reqs_cnt) == 1)
-		scsi_block_requests(hba->host);
+	blk_mq_unquiesce_tagset(&hba->host->tag_set);
  }

  static void ufshcd_add_cmd_upiu_trace(struct ufs_hba *hba, unsigned int tag,
@@ -10590,7 +10588,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)

  	/* Hold auto suspend until async scan completes */
  	pm_runtime_get_sync(dev);
-	atomic_set(&hba->scsi_block_reqs_cnt, 0);
+
  	/*
  	 * We are assuming that device wasn't put in sleep/power-down
  	 * state exclusively during the boot stage before kernel.
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 443afb97a637..58705994fc46 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -889,7 +889,6 @@ enum ufshcd_mcq_opr {
   * @wb_mutex: used to serialize devfreq and sysfs write booster toggling
   * @clk_scaling_lock: used to serialize device commands and clock scaling
   * @desc_size: descriptor sizes reported by device
- * @scsi_block_reqs_cnt: reference counting for scsi block requests
   * @bsg_dev: struct device associated with the BSG queue
   * @bsg_queue: BSG queue associated with the UFS controller
   * @rpm_dev_flush_recheck_work: used to suspend from RPM (runtime power
@@ -1050,7 +1049,6 @@ struct ufs_hba {

  	struct mutex wb_mutex;
  	struct rw_semaphore clk_scaling_lock;
-	atomic_t scsi_block_reqs_cnt;

  	struct device		bsg_dev;
  	struct request_queue	*bsg_queue;