scsi-disk: Switch to byte-based aio block access

Sector-based blk_aio_readv() and blk_aio_writev() should die; switch
to byte-based blk_aio_preadv() and blk_aio_pwritev() instead.

As part of the cleanup, scsi_init_iovec() no longer needs to return
a value, and reword a comment.

[ kwolf: Fix read accounting change ]
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/scsi/scsi-disk.c

@@ -108,7 +108,7 @@ static void scsi_check_condition(SCSIDiskReq *r, SCSISense sense)
     scsi_req_complete(&r->req, CHECK_CONDITION);
 }
 
-static uint32_t scsi_init_iovec(SCSIDiskReq *r, size_t size)
+static void scsi_init_iovec(SCSIDiskReq *r, size_t size)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
 
@@ -118,7 +118,6 @@ static uint32_t scsi_init_iovec(SCSIDiskReq *r, size_t size)
     }
     r->iov.iov_len = MIN(r->sector_count * 512, r->buflen);
     qemu_iovec_init_external(&r->qiov, &r->iov, 1);
-    return r->qiov.size / 512;
 }
 
 static void scsi_disk_save_request(QEMUFile *f, SCSIRequest *req)
@@ -316,7 +315,6 @@ done:
 static void scsi_do_read(SCSIDiskReq *r, int ret)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
-    uint32_t n;
 
     assert (r->req.aiocb == NULL);
 
@@ -340,11 +338,12 @@ static void scsi_do_read(SCSIDiskReq *r, int ret)
         r->req.aiocb = dma_blk_read(s->qdev.conf.blk, r->req.sg, r->sector,
                                     scsi_dma_complete, r);
     } else {
-        n = scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
+        scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
-                         n * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
-        r->req.aiocb = blk_aio_readv(s->qdev.conf.blk, r->sector, &r->qiov, n,
-                                     scsi_read_complete, r);
+                         r->qiov.size, BLOCK_ACCT_READ);
+        r->req.aiocb = blk_aio_preadv(s->qdev.conf.blk,
+                                      r->sector << BDRV_SECTOR_BITS, &r->qiov,
+                                      0, scsi_read_complete, r);
     }
 
 done:
@@ -504,7 +503,6 @@ static void scsi_write_data(SCSIRequest *req)
 {
     SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
-    uint32_t n;
 
     /* No data transfer may already be in progress */
     assert(r->req.aiocb == NULL);
@@ -544,11 +542,11 @@ static void scsi_write_data(SCSIRequest *req)
         r->req.aiocb = dma_blk_write(s->qdev.conf.blk, r->req.sg, r->sector,
                                      scsi_dma_complete, r);
     } else {
-        n = r->qiov.size / 512;
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
-                         n * BDRV_SECTOR_SIZE, BLOCK_ACCT_WRITE);
-        r->req.aiocb = blk_aio_writev(s->qdev.conf.blk, r->sector, &r->qiov, n,
-                                      scsi_write_complete, r);
+                         r->qiov.size, BLOCK_ACCT_WRITE);
+        r->req.aiocb = blk_aio_pwritev(s->qdev.conf.blk,
+                                       r->sector << BDRV_SECTOR_BITS, &r->qiov,
+                                       0, scsi_write_complete, r);
     }
 }
 
@@ -1730,13 +1728,13 @@ static void scsi_write_same_complete(void *opaque, int ret)
     if (data->iov.iov_len) {
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
                          data->iov.iov_len, BLOCK_ACCT_WRITE);
-        /* blk_aio_write doesn't like the qiov size being different from
-         * nb_sectors, make sure they match.
-         */
+        /* Reinitialize qiov, to handle unaligned WRITE SAME request
+         * where final qiov may need smaller size */
         qemu_iovec_init_external(&data->qiov, &data->iov, 1);
-        r->req.aiocb = blk_aio_writev(s->qdev.conf.blk, data->sector,
-                                      &data->qiov, data->iov.iov_len / 512,
-                                      scsi_write_same_complete, data);
+        r->req.aiocb = blk_aio_pwritev(s->qdev.conf.blk,
+                                       data->sector << BDRV_SECTOR_BITS,
+                                       &data->qiov, 0,
+                                       scsi_write_same_complete, data);
         return;
     }
 
@@ -1803,9 +1801,10 @@ static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf)
     scsi_req_ref(&r->req);
     block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
                      data->iov.iov_len, BLOCK_ACCT_WRITE);
-    r->req.aiocb = blk_aio_writev(s->qdev.conf.blk, data->sector,
-                                  &data->qiov, data->iov.iov_len / 512,
-                                  scsi_write_same_complete, data);
+    r->req.aiocb = blk_aio_pwritev(s->qdev.conf.blk,
+                                   data->sector << BDRV_SECTOR_BITS,
+                                   &data->qiov, 0,
+                                   scsi_write_same_complete, data);
 }
 
 static void scsi_disk_emulate_write_data(SCSIRequest *req)