scsi: megaraid_sas: Use struct_size() helper [Linux 5.3]

This Linux kernel change "scsi: megaraid_sas: Use struct_size() helper" is included in the Linux 5.3 release. This change is authored by Gustavo A. R. Silva <gustavo [at] embeddedor.com> on Fri Jun 7 13:40:53 2019 -0500. The commit for this change in Linux stable tree is e58ed50 (patch).

scsi: megaraid_sas: Use struct_size() helper

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some number of elements for that array. For example:

struct MR_PD_CFG_SEQ_NUM_SYNC {
    ...
        struct MR_PD_CFG_SEQ seq[1];
} __packed;

Make use of the struct_size() helper instead of an open-coded version in
order to avoid any potential type mistakes.

So, replace the following form:

sizeof(struct MR_PD_CFG_SEQ_NUM_SYNC) + (sizeof(struct MR_PD_CFG_SEQ) * (MAX_PHYSICAL_DEVICES - 1))

with:

struct_size(pd_sync, seq, MAX_PHYSICAL_DEVICES - 1)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/scsi/megaraid/megaraid_sas_fusion.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 2edb082..8a7ac5c 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -1203,7 +1203,7 @@ static int megasas_create_sg_sense_fusion(struct megasas_instance *instance)
 int
 megasas_sync_pd_seq_num(struct megasas_instance *instance, bool pend) {
    int ret = 0;
-   u32 pd_seq_map_sz;
+   size_t pd_seq_map_sz;
    struct megasas_cmd *cmd;
    struct megasas_dcmd_frame *dcmd;
    struct fusion_context *fusion = instance->ctrl_context;
@@ -1212,9 +1212,7 @@ static int megasas_create_sg_sense_fusion(struct megasas_instance *instance)

    pd_sync = (void *)fusion->pd_seq_sync[(instance->pd_seq_map_id & 1)];
    pd_seq_h = fusion->pd_seq_phys[(instance->pd_seq_map_id & 1)];
-   pd_seq_map_sz = sizeof(struct MR_PD_CFG_SEQ_NUM_SYNC) +
-           (sizeof(struct MR_PD_CFG_SEQ) *
-           (MAX_PHYSICAL_DEVICES - 1));
+   pd_seq_map_sz = struct_size(pd_sync, seq, MAX_PHYSICAL_DEVICES - 1);

    cmd = megasas_get_cmd(instance);
    if (!cmd) {

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