[PATCH v3 2/6] Drivers: hv: vmbus: Reduce number of references to message in vmbus_on_msg_dpc()

[Andrea Parri (Microsoft)]

Simplify the function by removing various references to the hv_message
'msg', introduce local variables 'msgtype' and 'payload_size'.

Suggested-by: Juan Vazquez <juv...@microsoft.com>
Suggested-by: Michael Kelley <mikel...@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.and...@gmail.com>
---
Changes since v2:
  - Squash patches #2 and #3
  - Revisit commit message

 drivers/hv/vmbus_drv.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 502f8cd95f6d4..44bcf9ccdaf5f 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1057,9 +1057,11 @@ void vmbus_on_msg_dpc(unsigned long data)
        struct hv_message *msg = (struct hv_message *)page_addr +
                                  VMBUS_MESSAGE_SINT;
        struct vmbus_channel_message_header *hdr;
+       enum vmbus_channel_message_type msgtype;
        const struct vmbus_channel_message_table_entry *entry;
        struct onmessage_work_context *ctx;
        u32 message_type = msg->header.message_type;
+       __u8 payload_size;
 
        /*
         * 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
@@ -1073,40 +1075,38 @@ void vmbus_on_msg_dpc(unsigned long data)
                return;
 
        hdr = (struct vmbus_channel_message_header *)msg->u.payload;
+       msgtype = hdr->msgtype;
 
        trace_vmbus_on_msg_dpc(hdr);
 
-       if (hdr->msgtype >= CHANNELMSG_COUNT) {
-               WARN_ONCE(1, "unknown msgtype=%d\n", hdr->msgtype);
+       if (msgtype >= CHANNELMSG_COUNT) {
+               WARN_ONCE(1, "unknown msgtype=%d\n", msgtype);
                goto msg_handled;
        }
 
-       if (msg->header.payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) {
-               WARN_ONCE(1, "payload size is too large (%d)\n",
-                         msg->header.payload_size);
+       payload_size = msg->header.payload_size;
+       if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) {
+               WARN_ONCE(1, "payload size is too large (%d)\n", payload_size);
                goto msg_handled;
        }
 
-       entry = &channel_message_table[hdr->msgtype];
+       entry = &channel_message_table[msgtype];
 
        if (!entry->message_handler)
                goto msg_handled;
 
-       if (msg->header.payload_size < entry->min_payload_len) {
-               WARN_ONCE(1, "message too short: msgtype=%d len=%d\n",
-                         hdr->msgtype, msg->header.payload_size);
+       if (payload_size < entry->min_payload_len) {
+               WARN_ONCE(1, "message too short: msgtype=%d len=%d\n", msgtype, 
payload_size);
                goto msg_handled;
        }
 
        if (entry->handler_type == VMHT_BLOCKING) {
-               ctx = kmalloc(sizeof(*ctx) + msg->header.payload_size,
-                             GFP_ATOMIC);
+               ctx = kmalloc(sizeof(*ctx) + payload_size, GFP_ATOMIC);
                if (ctx == NULL)
                        return;
 
                INIT_WORK(&ctx->work, vmbus_onmessage_work);
-               memcpy(&ctx->msg, msg, sizeof(msg->header) +
-                      msg->header.payload_size);
+               memcpy(&ctx->msg, msg, sizeof(msg->header) + payload_size);
 
                /*
                 * The host can generate a rescind message while we
@@ -1115,7 +1115,7 @@ void vmbus_on_msg_dpc(unsigned long data)
                 * by offer_in_progress and by channel_mutex.  See also the
                 * inline comments in vmbus_onoffer_rescind().
                 */
-               switch (hdr->msgtype) {
+               switch (msgtype) {
                case CHANNELMSG_RESCIND_CHANNELOFFER:
                        /*
                         * If we are handling the rescind message;
-- 
2.25.1