[PATCH] scsi: ufs: Fix some problems in task management request implementation

Can Guo
2021-01-20T10:25:49Z

Current task management request send/compl implementation is broken, the
problems and fixes are listed as below:

Problem: TMR completion timeout. ufshcd_tmc_handler() calls
blk_mq_tagset_busy_iter(fn == ufshcd_compl_tm()), but since
blk_mq_tagset_busy_iter() only iterates over all reserved tags and
started requests, so ufshcd_compl_tm() never gets a chance to run.
Fix: Call blk_mq_start_request() in __ufshcd_issue_tm_cmd().

Problem: Race condition in send/compl paths. ufshcd_compl_tm() looks for
all 0 bits in the REG_UTP_TASK_REQ_DOOR_BELL and call complete()
for each req who has the req->end_io_data set. There can be a race
condition btw tmc send/compl, because req->end_io_data is set, in
__ufshcd_issue_tm_cmd(), without host lock protection, so it is
possible that when ufshcd_compl_tm() checks the req->end_io_data,
req->end_io_data is set but the corresponding tag has not been set
in the REG_UTP_TASK_REQ_DOOR_BELL. Thus, ufshcd_tmc_handler() may
wrongly complete TMRs which have not been sent.
Fix: Protect req->end_io_data with host lock. And let ufshcd_compl_tm()
only handle those tm cmds which have been completed instead of
looking for 0 bits in the REG_UTP_TASK_REQ_DOOR_BELL.

Problem: In __ufshcd_issue_tm_cmd(), it is not right to use hba->nutrs +
req->tag as the Task Tag in one TMR UPIU.
Fix: Directly use req->tag as Task Tag.

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Can Guo <cang@codeaurora.org>

---

This change is based on Jaegeuk's change - https://git.kernel.org/mkp/scsi/c/eeb1b55b6e25

---

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index fb07e3a..44d09509 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -6252,7 +6252,7 @@ static irqreturn_t ufshcd_check_errors(struct ufs_hba *hba)

struct ctm_info {
struct ufs_hba *hba;
- unsigned long pending;
+ unsigned long completed;
unsigned int ncpl;
};

@@ -6261,13 +6261,13 @@ static bool ufshcd_compl_tm(struct request *req, void *priv, bool reserved)
struct ctm_info *const ci = priv;
struct completion *c;

- WARN_ON_ONCE(reserved);
- if (test_bit(req->tag, &ci->pending))
- return true;
- ci->ncpl++;
- c = req->end_io_data;
- if (c)
- complete(c);
+ if (test_bit(req->tag, &ci->completed)) {
+ __clear_bit(req->tag, &hba->outstanding_tasks);
+ ci->ncpl++;
+ c = req->end_io_data;
+ if (c)
+ complete(c);
+ }
return true;
}

@@ -6283,11 +6283,19 @@ static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
{
struct request_queue *q = hba->tmf_queue;
struct ctm_info ci = {
- .hba = hba,
- .pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL),
+ .hba = hba,
+ .ncpl = 0,
};
+ u32 tm_doorbell;
+ unsigned long completed;
+
+ tm_doorbell = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
+ completed = tm_doorbell ^ hba->outstanding_tasks;

- blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci);
+ if (completed) {
+ ci.completed = completed;
+ blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci);
+ }
return ci.ncpl ? IRQ_HANDLED : IRQ_NONE;
}

@@ -6405,37 +6413,33 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
DECLARE_COMPLETION_ONSTACK(wait);
struct request *req;
unsigned long flags;
- int free_slot, task_tag, err;
+ int task_tag, err;

/*
- * Get free slot, sleep if slots are unavailable.
- * Even though we use wait_event() which sleeps indefinitely,
- * the maximum wait time is bounded by %TM_CMD_TIMEOUT.
+ * blk_get_request() used here is only to get a free tag.
*/
req = blk_get_request(q, REQ_OP_DRV_OUT, 0);
if (IS_ERR(req))
return PTR_ERR(req);

- req->end_io_data = &wait;
- free_slot = req->tag;
- WARN_ON_ONCE(free_slot < 0 || free_slot >= hba->nutmrs);
ufshcd_hold(hba, false);
-
spin_lock_irqsave(host->host_lock, flags);
- task_tag = hba->nutrs + free_slot;
+ req->end_io_data = &wait;
+ blk_mq_start_request(req);

+ task_tag = req->tag;
treq->req_header.dword_0 |= cpu_to_be32(task_tag);

- memcpy(hba->utmrdl_base_addr + free_slot, treq, sizeof(*treq));
- ufshcd_vops_setup_task_mgmt(hba, free_slot, tm_function);
+ memcpy(hba->utmrdl_base_addr + task_tag, treq, sizeof(*treq));
+ ufshcd_vops_setup_task_mgmt(hba, task_tag, tm_function);

/* send command to the controller */
- __set_bit(free_slot, &hba->outstanding_tasks);
+ __set_bit(task_tag, &hba->outstanding_tasks);

/* Make sure descriptors are ready before ringing the task doorbell */
wmb();

- ufshcd_writel(hba, 1 << free_slot, REG_UTP_TASK_REQ_DOOR_BELL);
+ ufshcd_writel(hba, 1 << task_tag, REG_UTP_TASK_REQ_DOOR_BELL);
/* Make sure that doorbell is committed immediately */
wmb();

@@ -6447,32 +6451,33 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba *hba,
err = wait_for_completion_io_timeout(&wait,
msecs_to_jiffies(TM_CMD_TIMEOUT));
if (!err) {
+ spin_lock_irqsave(hba->host->host_lock, flags);
/*
* Make sure that ufshcd_compl_tm() does not trigger a
* use-after-free.
*/
req->end_io_data = NULL;
+ spin_unlock_irqrestore(hba->host->host_lock, flags);
ufshcd_add_tm_upiu_trace(hba, task_tag, "tm_complete_err");
dev_err(hba->dev, "%s: task management cmd 0x%.2x timed-out\n",
__func__, tm_function);
- if (ufshcd_clear_tm_cmd(hba, free_slot))
- dev_WARN(hba->dev, "%s: unable clear tm cmd (slot %d) after timeout\n",
- __func__, free_slot);
+ if (ufshcd_clear_tm_cmd(hba, task_tag)) {
+ dev_WARN(hba->dev, "%s: unable to clear tm cmd (slot %d) after timeout\n",
+ __func__, task_tag);
+ } else {
+ __clear_bit(task_tag, &hba->outstanding_tasks);
+ }
err = -ETIMEDOUT;
} else {
err = 0;
- memcpy(treq, hba->utmrdl_base_addr + free_slot, sizeof(*treq));
+ memcpy(treq, hba->utmrdl_base_addr + task_tag, sizeof(*treq));

ufshcd_add_tm_upiu_trace(hba, task_tag, "tm_complete");
}

- spin_lock_irqsave(hba->host->host_lock, flags);
- __clear_bit(free_slot, &hba->outstanding_tasks);
- spin_unlock_irqrestore(hba->host->host_lock, flags);
-
+ ufshcd_release(hba);
blk_put_request(req);

- ufshcd_release(hba);
return err;
}

--
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