Re: [PATCH v2][next] scsi: mpt3sas: Replace one-element array with flexible-array in struct _MPI2_CONFIG_PAGE_IO_UNIT_3

Gustavo A. R. Silva
2021-03-08T20:42:21Z

On Mon, Mar 08, 2021 at 12:12:59PM -0800, James Bottomley wrote:
> On Mon, 2021-03-08 at 13:32 -0600, Gustavo A. R. Silva wrote:
> > Hi all,
> >
> > Friendly ping: who can review/take this, please?
>
> Well, before embarking on a huge dynamic update, let's ask Broadcom the
> simpler question of why isn't MPI2_IO_UNIT_PAGE_3_GPIO_VAL_MAX simply
> set to 36? There's no dynamic allocation of anything in the current
> code ... it's all hard coded to allocate 36 entries. If there's no
> need for anything dynamic then the kzalloc could become

Yeah; and if that is the case, then there is no even need for kzalloc()
at all, and it can be replaced by memset():

diff --git a/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h b/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
index 43a3bf8ff428..d00431f553e1 100644
--- a/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
+++ b/drivers/scsi/mpt3sas/mpi/mpi2_cnfg.h
@@ -992,7 +992,7 @@ typedef struct _MPI2_CONFIG_PAGE_IO_UNIT_1 {
*one and check the value returned for GPIOCount at runtime.
*/
#ifndef MPI2_IO_UNIT_PAGE_3_GPIO_VAL_MAX
-#define MPI2_IO_UNIT_PAGE_3_GPIO_VAL_MAX (1)
+#define MPI2_IO_UNIT_PAGE_3_GPIO_VAL_MAX (36)
#endif

typedef struct _MPI2_CONFIG_PAGE_IO_UNIT_3 {
diff --git a/drivers/scsi/mpt3sas/mpt3sas_ctl.c b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
index 44f9a05db94e..23fcf29bfd67 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_ctl.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_ctl.c
@@ -3203,7 +3203,7 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
{
struct Scsi_Host *shost = class_to_shost(cdev);
struct MPT3SAS_ADAPTER *ioc = shost_priv(shost);
- Mpi2IOUnitPage3_t *io_unit_pg3 = NULL;
+ Mpi2IOUnitPage3_t io_unit_pg3;
Mpi2ConfigReply_t mpi_reply;
u16 backup_rail_monitor_status = 0;
u16 ioc_status;
@@ -3221,16 +3221,10 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
goto out;

/* allocate upto GPIOVal 36 entries */
- sz = offsetof(Mpi2IOUnitPage3_t, GPIOVal) + (sizeof(u16) * 36);
- io_unit_pg3 = kzalloc(sz, GFP_KERNEL);
- if (!io_unit_pg3) {
- rc = -ENOMEM;
- ioc_err(ioc, "%s: failed allocating memory for iounit_pg3: (%d) bytes\n",
- __func__, sz);
- goto out;
- }
+ sz = sizeof(io_unit_pg3);
+ memset(&io_unit_pg3, 0, sz);

- if (mpt3sas_config_get_iounit_pg3(ioc, &mpi_reply, io_unit_pg3, sz) !=
+ if (mpt3sas_config_get_iounit_pg3(ioc, &mpi_reply, &io_unit_pg3, sz) !=
0) {
ioc_err(ioc, "%s: failed reading iounit_pg3\n",
__func__);
@@ -3246,19 +3240,18 @@ BRM_status_show(struct device *cdev, struct device_attribute *attr,
goto out;
}

- if (io_unit_pg3->GPIOCount < 25) {
- ioc_err(ioc, "%s: iounit_pg3->GPIOCount less than 25 entries, detected (%d) entries\n",
- __func__, io_unit_pg3->GPIOCount);
+ if (io_unit_pg3.GPIOCount < 25) {
+ ioc_err(ioc, "%s: iounit_pg3.GPIOCount less than 25 entries, detected (%d) entries\n",
+ __func__, io_unit_pg3.GPIOCount);
rc = -EINVAL;
goto out;
}

/* BRM status is in bit zero of GPIOVal[24] */
- backup_rail_monitor_status = le16_to_cpu(io_unit_pg3->GPIOVal[24]);
+ backup_rail_monitor_status = le16_to_cpu(io_unit_pg3.GPIOVal[24]);
rc = snprintf(buf, PAGE_SIZE, "%d\n", (backup_rail_monitor_status & 1));

out:
- kfree(io_unit_pg3);
mutex_unlock(&ioc->pci_access_mutex);
return rc;
}

>
> io_unit_pg3 = kzalloc(sizeof(*io_unit_pg3), GFP_KERNEL);
>

Thanks
--
Gustavo