Re: [PATCH v2 1/1] scsi: qla2xxx: replace non-standard flexible array purex_item.iocb

Gustavo A. R. Silva
2025-07-29T02:20:54Z

On 28/07/25 19:37, Gustavo A. R. Silva wrote:
>
>> default item was replaced with the header and a static sized array,
>> cast to a purex_item * when returned through the alloc function
>>
>>    -       struct purex_item default_item;
>>    +       struct purex_item_hdr default_item;
>>    +       uint8_t __default_item_iocb[QLA_DEFAULT_PAYLOAD_SIZE];
>
> I see; yeah, this works as `(struct purex_item *)default_item->iocb`
> and `__default_item_iocb` happen to be just perfectly aligned. However,
> I wonder if there is any chance of this changing in the future...
>
> Probably, a code comment stating that both `(struct purex_item *)default_item->iocb`
> and `__default_item_iocb` are expected to share the same address would
> likely be helpful for anyone modifying something around this code in
> the future.
>
> BTW, instead of directly casting to `struct purex_item *`, you could
> use `container_of()` like this:
>
> item = container_of(&vha->default_item, struct purex_item, __hdr);
>
> but I guess that's up to maintainer's preference.
>

I just noticed that the new TRAILING_OVERLAP() helper just landed in
Linus' tree, and this issue seems to be a perfect candidate for it.

The (untested) patch below avoids the use of `struct_group_tagged()`
and the casts to `struct purex_item *`:

diff --git a/drivers/scsi/qla2xxx/qla_def.h b/drivers/scsi/qla2xxx/qla_def.h
index cb95b7b12051..4bdf8adf04ed 100644
--- a/drivers/scsi/qla2xxx/qla_def.h
+++ b/drivers/scsi/qla2xxx/qla_def.h
@@ -4890,9 +4890,7 @@ struct purex_item {
struct purex_item *pkt);
atomic_t in_use;
uint16_t size;
- struct {
- uint8_t iocb[64];
- } iocb;
+ uint8_t iocb[] __counted_by(size);
};

#include "qla_edif.h"
@@ -5101,7 +5099,6 @@ typedef struct scsi_qla_host {
struct list_head head;
spinlock_t lock;
} purex_list;
- struct purex_item default_item;

struct name_list_extended gnl;
/* Count of active session/fcport */
@@ -5130,6 +5127,10 @@ typedef struct scsi_qla_host {
#define DPORT_DIAG_IN_PROGRESS BIT_0
#define DPORT_DIAG_CHIP_RESET_IN_PROGRESS BIT_1
uint16_t dport_status;
+
+ TRAILING_OVERLAP(struct purex_item, default_item, iocb,
+ uint8_t __default_item_iocb[QLA_DEFAULT_PAYLOAD_SIZE];
+ );
} scsi_qla_host_t;

struct qla27xx_image_status {
diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index c4c6b5c6658c..4559b490614d 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -1077,17 +1077,17 @@ static struct purex_item *
qla24xx_alloc_purex_item(scsi_qla_host_t *vha, uint16_t size)
{
struct purex_item *item = NULL;
- uint8_t item_hdr_size = sizeof(*item);

if (size > QLA_DEFAULT_PAYLOAD_SIZE) {
- item = kzalloc(item_hdr_size +
- (size - QLA_DEFAULT_PAYLOAD_SIZE), GFP_ATOMIC);
+ item = kzalloc(struct_size(item, iocb, size), GFP_ATOMIC);
} else {
if (atomic_inc_return(&vha->default_item.in_use) == 1) {
item = &vha->default_item;
goto initialize_purex_header;
} else {
- item = kzalloc(item_hdr_size, GFP_ATOMIC);
+ item = kzalloc(
+ struct_size(item, iocb, QLA_DEFAULT_PAYLOAD_SIZE),
+ GFP_ATOMIC);
}
}
if (!item) {
@@ -1127,17 +1127,16 @@ qla24xx_queue_purex_item(scsi_qla_host_t *vha, struct purex_item *pkt,
* @vha: SCSI driver HA context
* @pkt: ELS packet
*/
-static struct purex_item
-*qla24xx_copy_std_pkt(struct scsi_qla_host *vha, void *pkt)
+static struct purex_item *
+qla24xx_copy_std_pkt(struct scsi_qla_host *vha, void *pkt)
{
struct purex_item *item;

- item = qla24xx_alloc_purex_item(vha,
- QLA_DEFAULT_PAYLOAD_SIZE);
+ item = qla24xx_alloc_purex_item(vha, QLA_DEFAULT_PAYLOAD_SIZE);
if (!item)
return item;

- memcpy(&item->iocb, pkt, sizeof(item->iocb));
+ memcpy(&item->iocb, pkt, QLA_DEFAULT_PAYLOAD_SIZE);
return item;
}

diff --git a/drivers/scsi/qla2xxx/qla_nvme.c b/drivers/scsi/qla2xxx/qla_nvme.c
index 8ee2e337c9e1..92488890bc04 100644
--- a/drivers/scsi/qla2xxx/qla_nvme.c
+++ b/drivers/scsi/qla2xxx/qla_nvme.c
@@ -1308,7 +1308,7 @@ void qla2xxx_process_purls_iocb(void **pkt, struct rsp_que **rsp)

ql_dbg(ql_dbg_unsol, vha, 0x2121,
"PURLS OP[%01x] size %d xchg addr 0x%x portid %06x\n",
- item->iocb.iocb[3], item->size, uctx->exchange_address,
+ item->iocb[3], item->size, uctx->exchange_address,
fcport->d_id.b24);
/* +48 0 1 2 3 4 5 6 7 8 9 A B C D E F
* ----- -----------------------------------------------
diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
index d4b484c0fd9d..253f802605d6 100644
--- a/drivers/scsi/qla2xxx/qla_os.c
+++ b/drivers/scsi/qla2xxx/qla_os.c
@@ -6459,9 +6459,10 @@ void qla24xx_process_purex_rdp(struct scsi_qla_host *vha,
void
qla24xx_free_purex_item(struct purex_item *item)
{
- if (item == &item->vha->default_item)
+ if (item == &item->vha->default_item) {
memset(&item->vha->default_item, 0, sizeof(struct purex_item));
- else
+ memset(&item->vha->__default_item_iocb, 0, QLA_DEFAULT_PAYLOAD_SIZE);
+ } else
kfree(item);

Thanks
-Gustavo