[PATCH] scsi: ufs: core: Quiesce SCSI devices instead of host tagset during error handling

[PATCH] scsi: ufs: core: Quiesce SCSI devices instead of host tagset during error handling

[Stanley Jhu]

Commit 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
switched UFS internal commands to allocate requests on
hba->host->pseudo_sdev->request_queue, which shares the host tagset with
regular LUNs.

During error recovery, ufshcd_err_handling_prepare() calls
blk_mq_quiesce_tagset(&hba->host->tag_set), marking all queues in the
tagset as quiesced, including pseudo_sdev->request_queue. When
ufshcd_verify_dev_init() subsequently issues internal commands (e.g. NOP
OUT UPIU) via blk_execute_rq(), blk_mq_run_hw_queue() skips running the
quiesced queue, resulting in an unrecoverable circular wait deadlock.

Resolve this by quiescing only logical units attached to the host via
shost_for_each_device() during error handling. Because
shost_for_each_device() explicitly skips pseudo SCSI devices (via
scsi_device_is_pseudo_dev() in __scsi_iterate_devices()), regular LUNs
are quiesced to prevent retry storms, while pseudo_sdev remains
unquiesced so internal commands can be dispatched and completed during
error recovery.

Clock scaling and command pause (ufshcd_pause_command_processing) paths
continue to use blk_mq_quiesce_tagset() as they require freezing all
queues including internal commands.

Fixes: 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/alpine.DEB.2.22.394.2609010729350.218556@hyperv.ins.bvanassche.us/
Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
---
 drivers/ufs/core/ufshcd.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 2ba244cf40ac..11488c5efb47 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -6798,6 +6798,23 @@ static void ufshcd_clk_scaling_suspend(struct ufs_hba *hba, bool suspend)
 	}
 }
 
+static void ufshcd_quiesce_all_sdevs(struct ufs_hba *hba)
+{
+	struct scsi_device *sdev;
+
+	shost_for_each_device(sdev, hba->host)
+		blk_mq_quiesce_queue_nowait(sdev->request_queue);
+	blk_mq_wait_quiesce_done(&hba->host->tag_set);
+}
+
+static void ufshcd_unquiesce_all_sdevs(struct ufs_hba *hba)
+{
+	struct scsi_device *sdev;
+
+	shost_for_each_device(sdev, hba->host)
+		blk_mq_unquiesce_queue(sdev->request_queue);
+}
+
 static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 {
 	/*
@@ -6833,7 +6850,7 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 		ufshcd_clk_scaling_allow(hba, false);
 	}
 	/* Wait for ongoing ufshcd_queuecommand() calls to finish. */
-	blk_mq_quiesce_tagset(&hba->host->tag_set);
+	ufshcd_quiesce_all_sdevs(hba);
 	cancel_work_sync(&hba->eeh_work);
 }
 
@@ -6840,7 +6857,7 @@ static void ufshcd_err_handling_prepare(struct ufs_hba *hba)
 static void ufshcd_err_handling_unprepare(struct ufs_hba *hba)
 {
-	blk_mq_unquiesce_tagset(&hba->host->tag_set);
+	ufshcd_unquiesce_all_sdevs(hba);
 	ufshcd_release(hba);
 	if (ufshcd_is_clkscaling_supported(hba))
 		ufshcd_clk_scaling_suspend(hba, false);
-- 
2.43.0

Re: [PATCH] scsi: ufs: core: Quiesce SCSI devices instead of host tagset during error handling

[Bart Van Assche]

On 9/2/26 1:23 AM, Stanley Jhu wrote:
> Commit 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
> switched UFS internal commands to allocate requests on
> hba->host->pseudo_sdev->request_queue, which shares the host tagset with
> regular LUNs.
> 
> During error recovery, ufshcd_err_handling_prepare() calls
> blk_mq_quiesce_tagset(&hba->host->tag_set), marking all queues in the
> tagset as quiesced, including pseudo_sdev->request_queue. When
> ufshcd_verify_dev_init() subsequently issues internal commands (e.g. NOP
> OUT UPIU) via blk_execute_rq(), blk_mq_run_hw_queue() skips running the
> quiesced queue, resulting in an unrecoverable circular wait deadlock.
> 
> Resolve this by quiescing only logical units attached to the host via
> shost_for_each_device() during error handling. Because
> shost_for_each_device() explicitly skips pseudo SCSI devices (via
> scsi_device_is_pseudo_dev() in __scsi_iterate_devices()), regular LUNs
> are quiesced to prevent retry storms, while pseudo_sdev remains
> unquiesced so internal commands can be dispatched and completed during
> error recovery.
> 
> Clock scaling and command pause (ufshcd_pause_command_processing) paths
> continue to use blk_mq_quiesce_tagset() as they require freezing all
> queues including internal commands.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>