2022-01-04 13:07:32

by Wenchao Hao

Subject: [PATCH demo] ata_scsi_queuecmd: Make input parameters check more clearly

This is just a clean code. Since each branch of "if" state would check
scmd->cmd_len, so move the check of scmd->cmd_len out of "if" state to
simplify the logic of input parameters check.

The patch do not change origin function logic.

Signed-off-by: Wenchao Hao <[email protected]>
---
drivers/ata/libata-scsi.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 313e9475507b..1c653b5327db 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -4020,19 +4020,18 @@ void ata_scsi_dump_cdb(struct ata_port *ap, struct scsi_cmnd *cmd)
int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
{
u8 scsi_op = scmd->cmnd[0];
- ata_xlat_func_t xlat_func;
+ ata_xlat_func_t xlat_func = NULL;
int rc = 0;

+ if (unlikely(!scmd->cmd_len))
+ goto bad_cdb_len;
+
if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
- if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
+ if (unlikely(scmd->cmd_len > dev->cdb_len))
goto bad_cdb_len;

xlat_func = ata_get_xlat_func(dev, scsi_op);
} else {
- if (unlikely(!scmd->cmd_len))
- goto bad_cdb_len;
-
- xlat_func = NULL;
if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
/* relay SCSI command to ATAPI device */
int len = COMMAND_SIZE(scsi_op);
--
2.32.0

2022-01-05 05:59:43

by Damien Le Moal

Subject: Re: [PATCH demo] ata_scsi_queuecmd: Make input parameters check more clearly

On 1/5/22 11:17, Wenchao Hao wrote:
> This is just a clean code. Since each branch of "if" state would check
> scmd->cmd_len, so move the check of scmd->cmd_len out of "if" state to
> simplify the logic of input parameters check.
>
> The patch do not change origin function logic.
>
> Signed-off-by: Wenchao Hao <[email protected]>
> ---
> drivers/ata/libata-scsi.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 313e9475507b..1c653b5327db 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -4020,19 +4020,18 @@ void ata_scsi_dump_cdb(struct ata_port *ap, struct scsi_cmnd *cmd)
> int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
> {
> u8 scsi_op = scmd->cmnd[0];
> - ata_xlat_func_t xlat_func;
> + ata_xlat_func_t xlat_func = NULL;

Not needed. xlat_func is always set for the non-error cases.

> int rc = 0;
>
> + if (unlikely(!scmd->cmd_len))
> + goto bad_cdb_len;
> +
> if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
> - if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
> + if (unlikely(scmd->cmd_len > dev->cdb_len))
> goto bad_cdb_len;
>
> xlat_func = ata_get_xlat_func(dev, scsi_op);
> } else {
> - if (unlikely(!scmd->cmd_len))
> - goto bad_cdb_len;
> -
> - xlat_func = NULL;
> if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
> /* relay SCSI command to ATAPI device */
> int len = COMMAND_SIZE(scsi_op);

I would go further and cleanup the if else { if else } sequence too.
Something like this:

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a16ef0030667..ed8be585a98f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3958,42 +3958,39 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
struct ata_device *dev)
{
u8 scsi_op = scmd->cmnd[0];
ata_xlat_func_t xlat_func;
- int rc = 0;
+
+ if (unlikely(!scmd->cmd_len))
+ goto bad_cdb_len;

if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
- if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
+ if (unlikely(scmd->cmd_len > dev->cdb_len))
goto bad_cdb_len;

xlat_func = ata_get_xlat_func(dev, scsi_op);
- } else {
- if (unlikely(!scmd->cmd_len))
- goto bad_cdb_len;
+ } else if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
+ /* relay SCSI command to ATAPI device */
+ int len = COMMAND_SIZE(scsi_op);

- xlat_func = NULL;
- if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
- /* relay SCSI command to ATAPI device */
- int len = COMMAND_SIZE(scsi_op);
- if (unlikely(len > scmd->cmd_len ||
- len > dev->cdb_len ||
- scmd->cmd_len > ATAPI_CDB_LEN))
- goto bad_cdb_len;
+ if (unlikely(len > scmd->cmd_len ||
+ len > dev->cdb_len ||
+ scmd->cmd_len > ATAPI_CDB_LEN))
+ goto bad_cdb_len;

- xlat_func = atapi_xlat;
- } else {
- /* ATA_16 passthru, treat as an ATA command */
- if (unlikely(scmd->cmd_len > 16))
- goto bad_cdb_len;
+ xlat_func = atapi_xlat;
+ } else {
+ /* ATA_16 passthru, treat as an ATA command */
+ if (unlikely(scmd->cmd_len > 16))
+ goto bad_cdb_len;

- xlat_func = ata_get_xlat_func(dev, scsi_op);
- }
+ xlat_func = ata_get_xlat_func(dev, scsi_op);
}

if (xlat_func)
- rc = ata_scsi_translate(dev, scmd, xlat_func);
- else
- ata_scsi_simulate(dev, scmd);
+ return ata_scsi_translate(dev, scmd, xlat_func);

- return rc;
+ ata_scsi_simulate(dev, scmd);
+
+ return 0;

bad_cdb_len:
scmd->result = DID_ERROR << 16;






--
Damien Le Moal
Western Digital Research

2022-01-05 06:04:25

by Damien Le Moal

Subject: Re: [PATCH demo] ata_scsi_queuecmd: Make input parameters check more clearly

Resending my reply as the server mx5.huawei.com bounces back to me all my
emails from @opensource.wdc.com... (error 554, but SPF record is correct !)


On Tue, 2022-01-04 at 21:17 -0500, Wenchao Hao wrote:
> This is just a clean code. Since each branch of "if" state would check
> scmd->cmd_len, so move the check of scmd->cmd_len out of "if" state to
> simplify the logic of input parameters check.
>
> The patch do not change origin function logic.
>
> Signed-off-by: Wenchao Hao <[email protected]>
> ---
> drivers/ata/libata-scsi.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 313e9475507b..1c653b5327db 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -4020,19 +4020,18 @@ void ata_scsi_dump_cdb(struct ata_port *ap, struct scsi_cmnd *cmd)
> int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
> {
> u8 scsi_op = scmd->cmnd[0];
> - ata_xlat_func_t xlat_func;
> + ata_xlat_func_t xlat_func = NULL;

Not needed. xlat_func is always set for the non-error cases.

> int rc = 0;
>
> + if (unlikely(!scmd->cmd_len))
> + goto bad_cdb_len;
> +
> if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
> - if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
> + if (unlikely(scmd->cmd_len > dev->cdb_len))
> goto bad_cdb_len;
>
> xlat_func = ata_get_xlat_func(dev, scsi_op);
> } else {
> - if (unlikely(!scmd->cmd_len))
> - goto bad_cdb_len;
> -
> - xlat_func = NULL;
> if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
> /* relay SCSI command to ATAPI device */
> int len = COMMAND_SIZE(scsi_op);

I would go further and cleanup the if else { if else } sequence too.
Something like this:

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a16ef0030667..ed8be585a98f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3958,42 +3958,39 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
struct ata_device *dev)
{
u8 scsi_op = scmd->cmnd[0];
ata_xlat_func_t xlat_func;
- int rc = 0;
+
+ if (unlikely(!scmd->cmd_len))
+ goto bad_cdb_len;

if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
- if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
+ if (unlikely(scmd->cmd_len > dev->cdb_len))
goto bad_cdb_len;

xlat_func = ata_get_xlat_func(dev, scsi_op);
- } else {
- if (unlikely(!scmd->cmd_len))
- goto bad_cdb_len;
+ } else if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
+ /* relay SCSI command to ATAPI device */
+ int len = COMMAND_SIZE(scsi_op);

- xlat_func = NULL;
- if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
- /* relay SCSI command to ATAPI device */
- int len = COMMAND_SIZE(scsi_op);
- if (unlikely(len > scmd->cmd_len ||
- len > dev->cdb_len ||
- scmd->cmd_len > ATAPI_CDB_LEN))
- goto bad_cdb_len;
+ if (unlikely(len > scmd->cmd_len ||
+ len > dev->cdb_len ||
+ scmd->cmd_len > ATAPI_CDB_LEN))
+ goto bad_cdb_len;

- xlat_func = atapi_xlat;
- } else {
- /* ATA_16 passthru, treat as an ATA command */
- if (unlikely(scmd->cmd_len > 16))
- goto bad_cdb_len;
+ xlat_func = atapi_xlat;
+ } else {
+ /* ATA_16 passthru, treat as an ATA command */
+ if (unlikely(scmd->cmd_len > 16))
+ goto bad_cdb_len;

- xlat_func = ata_get_xlat_func(dev, scsi_op);
- }
+ xlat_func = ata_get_xlat_func(dev, scsi_op);
}

if (xlat_func)
- rc = ata_scsi_translate(dev, scmd, xlat_func);
- else
- ata_scsi_simulate(dev, scmd);
+ return ata_scsi_translate(dev, scmd, xlat_func);

- return rc;
+ ata_scsi_simulate(dev, scmd);
+
+ return 0;

bad_cdb_len:
scmd->result = DID_ERROR << 16;

Also please change the patch title prefix to: "ata: libata-scsi: ...."

--
Damien Le Moal
Western Digital Research