[Qemu-devel] [PULL 16/69] vdi: Implement .bdrv_co_preadv() interface

[Kevin Wolf <kwolf@redhat.com>]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
---
 block/vdi.c | 55 ++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index 75d4819..8295511 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -557,48 +557,57 @@ static int64_t coroutine_fn vdi_co_get_block_status(BlockDriverState *bs,
     return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | offset;
 }
 
-static int vdi_co_read(BlockDriverState *bs,
-        int64_t sector_num, uint8_t *buf, int nb_sectors)
+static int coroutine_fn
+vdi_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+              QEMUIOVector *qiov, int flags)
 {
     BDRVVdiState *s = bs->opaque;
+    QEMUIOVector local_qiov;
     uint32_t bmap_entry;
     uint32_t block_index;
-    uint32_t sector_in_block;
-    uint32_t n_sectors;
+    uint32_t offset_in_block;
+    uint32_t n_bytes;
+    uint64_t bytes_done = 0;
     int ret = 0;
 
     logout("\n");
 
-    while (ret >= 0 && nb_sectors > 0) {
-        block_index = sector_num / s->block_sectors;
-        sector_in_block = sector_num % s->block_sectors;
-        n_sectors = s->block_sectors - sector_in_block;
-        if (n_sectors > nb_sectors) {
-            n_sectors = nb_sectors;
-        }
+    qemu_iovec_init(&local_qiov, qiov->niov);
 
-        logout("will read %u sectors starting at sector %" PRIu64 "\n",
-               n_sectors, sector_num);
+    while (ret >= 0 && bytes > 0) {
+        block_index = offset / s->block_size;
+        offset_in_block = offset % s->block_size;
+        n_bytes = MIN(bytes, s->block_size - offset_in_block);
+
+        logout("will read %u bytes starting at offset %" PRIu64 "\n",
+               n_bytes, offset);
 
         /* prepare next AIO request */
         bmap_entry = le32_to_cpu(s->bmap[block_index]);
         if (!VDI_IS_ALLOCATED(bmap_entry)) {
             /* Block not allocated, return zeros, no need to wait. */
-            memset(buf, 0, n_sectors * SECTOR_SIZE);
+            qemu_iovec_memset(qiov, bytes_done, 0, n_bytes);
             ret = 0;
         } else {
-            uint64_t offset = s->header.offset_data / SECTOR_SIZE +
-                              (uint64_t)bmap_entry * s->block_sectors +
-                              sector_in_block;
-            ret = bdrv_read(bs->file->bs, offset, buf, n_sectors);
+            uint64_t data_offset = s->header.offset_data +
+                                   (uint64_t)bmap_entry * s->block_size +
+                                   offset_in_block;
+
+            qemu_iovec_reset(&local_qiov);
+            qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);
+
+            ret = bdrv_co_preadv(bs->file->bs, data_offset, n_bytes,
+                                 &local_qiov, 0);
         }
-        logout("%u sectors read\n", n_sectors);
+        logout("%u bytes read\n", n_bytes);
 
-        nb_sectors -= n_sectors;
-        sector_num += n_sectors;
-        buf += n_sectors * SECTOR_SIZE;
+        bytes -= n_bytes;
+        offset += n_bytes;
+        bytes_done += n_bytes;
     }
 
+    qemu_iovec_destroy(&local_qiov);
+
     return ret;
 }
 
@@ -903,7 +912,7 @@ static BlockDriver bdrv_vdi = {
     .bdrv_co_get_block_status = vdi_co_get_block_status,
     .bdrv_make_empty = vdi_make_empty,
 
-    .bdrv_read = vdi_co_read,
+    .bdrv_co_preadv     = vdi_co_preadv,
 #if defined(CONFIG_VDI_WRITE)
     .bdrv_write = vdi_co_write,
 #endif
-- 
1.8.3.1