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Subject[PATCH v4 2/3] scsi: ufs: Fix a race condition between ufshcd_abort and eh_work
Date
In current task abort routine, if task abort happens to the device W-LU,
the code directly jumps to ufshcd_eh_host_reset_handler() to perform a
full reset and restore then returns FAIL or SUCCESS. Commands sent to the
device W-LU are most likely the SSU cmds sent during UFS PM operations. If
such SSU cmd enters task abort routine, when ufshcd_eh_host_reset_handler()
flushes eh_work, it will get stuck there since err_handler is serialized
with PM operations.

In order to unblock above call path, we merely clean up the lrb taken by
this cmd, queue the eh_work and return SUCCESS. Once the cmd is aborted,
the PM operation which sends out the cmd just errors out, then err_handler
shall be able to proceed with the full reset and restore.

In this scenario, the cmd is aborted even before it is actually cleared by
HW, set the lrb->in_use flag to prevent subsequent cmds, including SCSI
cmds and dev cmds, from taking the lrb released from abort. The flag shall
evetually be cleared in __ufshcd_transfer_req_compl() invoked by the full
reset and restore from err_handler.

Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
---
drivers/scsi/ufs/ufshcd.c | 55 ++++++++++++++++++++++++++++++++++++-----------
drivers/scsi/ufs/ufshcd.h | 2 ++
2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 7e764e8..cd7394e 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2539,6 +2539,14 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
(hba->clk_gating.state != CLKS_ON));

lrbp = &hba->lrb[tag];
+ if (unlikely(lrbp->in_use)) {
+ if (hba->pm_op_in_progress)
+ set_host_byte(cmd, DID_BAD_TARGET);
+ else
+ err = SCSI_MLQUEUE_HOST_BUSY;
+ ufshcd_release(hba);
+ goto out;
+ }

WARN_ON(lrbp->cmd);
lrbp->cmd = cmd;
@@ -2781,6 +2789,11 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,

init_completion(&wait);
lrbp = &hba->lrb[tag];
+ if (unlikely(lrbp->in_use)) {
+ err = -EBUSY;
+ goto out;
+ }
+
WARN_ON(lrbp->cmd);
err = ufshcd_compose_dev_cmd(hba, lrbp, cmd_type, tag);
if (unlikely(err))
@@ -2797,6 +2810,7 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,

err = ufshcd_wait_for_dev_cmd(hba, lrbp, timeout);

+out:
ufshcd_add_query_upiu_trace(hba, tag,
err ? "query_complete_err" : "query_complete");

@@ -4932,6 +4946,7 @@ static void __ufshcd_transfer_req_compl(struct ufs_hba *hba,

for_each_set_bit(index, &completed_reqs, hba->nutrs) {
lrbp = &hba->lrb[index];
+ lrbp->in_use = false;
lrbp->compl_time_stamp = ktime_get();
cmd = lrbp->cmd;
if (cmd) {
@@ -6374,8 +6389,12 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,

init_completion(&wait);
lrbp = &hba->lrb[tag];
- WARN_ON(lrbp->cmd);
+ if (unlikely(lrbp->in_use)) {
+ err = -EBUSY;
+ goto out;
+ }

+ WARN_ON(lrbp->cmd);
lrbp->cmd = NULL;
lrbp->sense_bufflen = 0;
lrbp->sense_buffer = NULL;
@@ -6447,6 +6466,7 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
}
}

+out:
blk_put_request(req);
out_unlock:
up_read(&hba->clk_scaling_lock);
@@ -6696,16 +6716,6 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
BUG();
}

- /*
- * Task abort to the device W-LUN is illegal. When this command
- * will fail, due to spec violation, scsi err handling next step
- * will be to send LU reset which, again, is a spec violation.
- * To avoid these unnecessary/illegal step we skip to the last error
- * handling stage: reset and restore.
- */
- if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN)
- return ufshcd_eh_host_reset_handler(cmd);
-
ufshcd_hold(hba, false);
reg = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
/* If command is already aborted/completed, return SUCCESS */
@@ -6726,7 +6736,7 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
* to reduce repeated printouts. For other aborted requests only print
* basic details.
*/
- scsi_print_command(hba->lrb[tag].cmd);
+ scsi_print_command(cmd);
if (!hba->req_abort_count) {
ufshcd_update_reg_hist(&hba->ufs_stats.task_abort, 0);
ufshcd_print_host_regs(hba);
@@ -6745,6 +6755,27 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
goto cleanup;
}

+ /*
+ * Task abort to the device W-LUN is illegal. When this command
+ * will fail, due to spec violation, scsi err handling next step
+ * will be to send LU reset which, again, is a spec violation.
+ * To avoid these unnecessary/illegal steps, first we clean up
+ * the lrb taken by this cmd and mark the lrb as in_use, then
+ * queue the eh_work and bail.
+ */
+ if (lrbp->lun == UFS_UPIU_UFS_DEVICE_WLUN) {
+ spin_lock_irqsave(host->host_lock, flags);
+ if (lrbp->cmd) {
+ __ufshcd_transfer_req_compl(hba, (1UL << tag));
+ __set_bit(tag, &hba->outstanding_reqs);
+ lrbp->in_use = true;
+ hba->force_reset = true;
+ ufshcd_schedule_eh_work(hba);
+ }
+ spin_unlock_irqrestore(host->host_lock, flags);
+ goto out;
+ }
+
/* Skip task abort in case previous aborts failed and report failure */
if (lrbp->req_abort_skip)
err = -EIO;
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 1e680bf..66e5338 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -163,6 +163,7 @@ struct ufs_pm_lvl_states {
* @crypto_key_slot: the key slot to use for inline crypto (-1 if none)
* @data_unit_num: the data unit number for the first block for inline crypto
* @req_abort_skip: skip request abort task flag
+ * @in_use: indicates that this lrb is still in use
*/
struct ufshcd_lrb {
struct utp_transfer_req_desc *utr_descriptor_ptr;
@@ -192,6 +193,7 @@ struct ufshcd_lrb {
#endif

bool req_abort_skip;
+ bool in_use;
};

/**
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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