[Qemu-devel] [PATCH 3/4] Refactor scsi-disk layer for queue'ing writes

[Ryan Harper <ryanh@us.ibm.com>]

Refactor scsi write path to match the simpler, faster scsi read path.  No need
to call into the write completion function to calculate the request buf length.

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>

diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 16b3215..f2b4814 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -208,25 +208,14 @@ static void scsi_write_complete(void * opaque, int ret)
 {
     SCSIRequest *r = (SCSIRequest *)opaque;
     SCSIDeviceState *s = r->dev;
-    uint32_t len;
 
     if (ret) {
         fprintf(stderr, "scsi-disc: IO write error\n");
         exit(1);
     }
-
     r->aiocb = NULL;
-    if (r->sector_count == 0) {
-        scsi_command_complete(r, SENSE_NO_SENSE);
-    } else {
-        len = r->sector_count * 512;
-        if (len > SCSI_DMA_BUF_SIZE) {
-            len = SCSI_DMA_BUF_SIZE;
-        }
-        r->buf_len = len;
-        DPRINTF("Write complete tag=0x%x more=%d\n", r->tag, len);
-        s->completion(s->opaque, SCSI_REASON_DATA, r->tag, len);
-    }
+    DPRINTF("Write complete tag=0x%x more=%d\n", r->tag, r->buf_len);
+    s->completion(s->opaque, SCSI_REASON_DATA, r->tag, r->buf_len);
 }
 
 /* Write data to a scsi device.  Returns nonzero on failure.
@@ -235,7 +224,7 @@ static int scsi_write_data(SCSIDevice *d, uint32_t tag)
 {
     SCSIDeviceState *s = d->state;
     SCSIRequest *r;
-    uint32_t n;
+    uint32_t n, len;
 
     DPRINTF("Write data tag=0x%x\n", tag);
     r = scsi_find_request(s, tag);
@@ -244,8 +233,22 @@ static int scsi_write_data(SCSIDevice *d, uint32_t tag)
         scsi_command_complete(r, SENSE_HARDWARE_ERROR);
         return 1;
     }
+    DPRINTF("Write sector_count=%d\n", r->sector_count);
+    if (r->sector_count == 0) {
+        scsi_command_complete(r, SENSE_NO_SENSE);
+        return 0;
+    }
     if (r->aiocb)
         BADF("Data transfer already in progress\n");
+
+    /* we know the len of the request and with the max size of the scsi buffer,
+     * we can calculate buf_len needed */
+    len = r->sector_count * 512;
+    if (len > SCSI_DMA_BUF_SIZE)
+        len = SCSI_DMA_BUF_SIZE;
+    r->buf_len = len;
+
+    /* number of sectors to submit */
     n = r->buf_len / 512;
     if (n) {
         r->aiocb = bdrv_aio_write(s->bdrv, r->sector, r->dma_buf, n,