On 2023/9/22 20:50, Damien Le Moal wrote:
On 2023/09/22 2:38, Wenchao Hao wrote:
This is just a cleanup for scsi_dev_queue_ready() to avoid
redundant goto and if statement, it did not change the origin
logic.
Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 35 ++++++++++++++++++-----------------
1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index ca5eb058d5c7..f3e388127dbd 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1254,28 +1254,29 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
int token;
token = sbitmap_get(&sdev->budget_map);
- if (atomic_read(&sdev->device_blocked)) {
- if (token < 0)
- goto out;
+ if (token < 0)
+ return -1;
This is changing how this function works...
I don't think so...
The origin function flow:
static inline int scsi_dev_queue_ready(struct request_queue *q,
struct scsi_device *sdev)
{
...
token = sbitmap_get(&sdev->budget_map);
if (atomic_read(&sdev->device_blocked)) {
if (token < 0)
goto out;
}
return token;
out:
return -1
}
If the token is less than 0, it would always return -1. So we can found
it's not necessary to check token after atomic_read().
- if (scsi_device_busy(sdev) > 1)
- goto out_dec;
+ /*
+ * device_blocked is not set at mostly time, so check it first
+ * and return token when it is not set.
+ */
+ if (!atomic_read(&sdev->device_blocked))
+ return token;
...because you reversed the tests order.
As explained in comment, the device_blocked is not set at mostly time,
so when it's not set, just return the token.
- /*
- * unblock after device_blocked iterates to zero
- */
- if (atomic_dec_return(&sdev->device_blocked) > 0)
- goto out_dec;
- SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
- "unblocking device at zero depth\n"));
+ /*
+ * unblock after device_blocked iterates to zero
+ */
+ if (scsi_device_busy(sdev) > 1 ||
+ atomic_dec_return(&sdev->device_blocked) > 0) {
And here too, you are changing how the function works. The atomic_dec may not be
done if the first condition is true.
the origin flow would not call atomic_dec_return() too when condition
"scsi_device_busy(sdev) > 1" is true like following:
static inline int scsi_dev_queue_ready(struct request_queue *q,
struct scsi_device *sdev)
{
...
if (atomic_read(&sdev->device_blocked)) {
if (scsi_device_busy(sdev) > 1)
goto out_dec;
/*
* unblock after device_blocked iterates to zero
*/
if (atomic_dec_return(&sdev->device_blocked) > 0)
goto out_dec;
SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
"unblocking device at zero depth\n"));
}
return token;
out_dec:
if (token >= 0)
sbitmap_put(&sdev->budget_map, token);
out:
return -1;
}
Here is the function before and after my change:
The old function:
static inline int scsi_dev_queue_ready(struct request_queue *q,
struct scsi_device *sdev)
{
int token;
token = sbitmap_get(&sdev->budget_map);
if (token < 0)
return -1;
/*
* device_blocked is not set at mostly time, so check it first
* and return token when it is not set.
*/
if (!atomic_read(&sdev->device_blocked))
return token;
/*
* unblock after device_blocked iterates to zero
*/
if (scsi_device_busy(sdev) > 1 ||
atomic_dec_return(&sdev->device_blocked) > 0) {
sbitmap_put(&sdev->budget_map, token);
return -1;
}
SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
"unblocking device at zero depth\n"));
return token;
}
Function after my change:
static inline int scsi_dev_queue_ready(struct request_queue *q,
struct scsi_device *sdev)
{
int token;
token = sbitmap_get(&sdev->budget_map);
if (token < 0)
return -1;
/*
* device_blocked is not set at mostly time, so check it first
* and return token when it is not set.
*/
if (!atomic_read(&sdev->device_blocked))
return token;
/*
* unblock after device_blocked iterates to zero
*/
if (scsi_device_busy(sdev) > 1 ||
atomic_dec_return(&sdev->device_blocked) > 0) {
sbitmap_put(&sdev->budget_map, token);
return -1;
}
SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
"unblocking device at zero depth\n"));
return token;
}
I think it looks more clear and readable than before.
+ sbitmap_put(&sdev->budget_map, token);
+ return -1;
}
+ SCSI_LOG_MLQUEUE(3, sdev_printk(KERN_INFO, sdev,
+ "unblocking device at zero depth\n"));
+
return token;
-out_dec:
- if (token >= 0)
- sbitmap_put(&sdev->budget_map, token);
-out:
- return -1;
}
/*
