scsi: ufs: core: Fix ufshcd_abort_one racing issue

When ufshcd_abort_one is racing with the completion ISR, the completed tag
of the request's mq_hctx pointer will be set to NULL by ISR.  Return
success when request is completed by ISR because ufshcd_abort_one does not
need to do anything.

The racing flow is:

Thread A
ufshcd_err_handler					step 1
	...
	ufshcd_abort_one
		ufshcd_try_to_abort_task
			ufshcd_cmd_inflight(true)	step 3
		ufshcd_mcq_req_to_hwq
			blk_mq_unique_tag
				rq->mq_hctx->queue_num	step 5

Thread B
ufs_mtk_mcq_intr(cq complete ISR)			step 2
	scsi_done
		...
		__blk_mq_free_request
			rq->mq_hctx = NULL;		step 4

Below is KE back trace.
  ufshcd_try_to_abort_task: cmd at tag 41 not pending in the device.
  ufshcd_try_to_abort_task: cmd at tag=41 is cleared.
  Aborting tag 41 / CDB 0x28 succeeded
  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000194
  pc : [0xffffffddd7a79bf8] blk_mq_unique_tag+0x8/0x14
  lr : [0xffffffddd6155b84] ufshcd_mcq_req_to_hwq+0x1c/0x40 [ufs_mediatek_mod_ise]
   do_mem_abort+0x58/0x118
   el1_abort+0x3c/0x5c
   el1h_64_sync_handler+0x54/0x90
   el1h_64_sync+0x68/0x6c
   blk_mq_unique_tag+0x8/0x14
   ufshcd_err_handler+0xae4/0xfa8 [ufs_mediatek_mod_ise]
   process_one_work+0x208/0x4fc
   worker_thread+0x228/0x438
   kthread+0x104/0x1d4
   ret_from_fork+0x10/0x20

Fixes: 93e6c0e ("scsi: ufs: core: Clear cmd if abort succeeds in MCQ mode")
Suggested-by: Bart Van Assche <[email protected]>
Signed-off-by: Peter Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Bart Van Assche <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

Author: ptr324

drivers/ufs/core/ufshcd.c

@@ -6456,6 +6456,8 @@ static bool ufshcd_abort_one(struct request *rq, void *priv)
 	/* Release cmd in MCQ mode if abort succeeds */
 	if (is_mcq_enabled(hba) && (*ret == 0)) {
 		hwq = ufshcd_mcq_req_to_hwq(hba, scsi_cmd_to_rq(lrbp->cmd));
+		if (!hwq)
+			return 0;
 		spin_lock_irqsave(&hwq->cq_lock, flags);
 		if (ufshcd_cmd_inflight(lrbp->cmd))
 			ufshcd_release_scsi_cmd(hba, lrbp);