vpc: Read/write multiple sectors at once

This changes the vpc block driver (for VHD) to read/write multiple sectors at
once instead of doing a request for each single sector.

Before this, running qemu-iotests for VPC took ages, now it's actually quite
reasonable to run it always (down from ~1 hour to 40 seconds for me).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/vpc.c

@@ -371,23 +371,33 @@ fail:
 static int vpc_read(BlockDriverState *bs, int64_t sector_num,
                     uint8_t *buf, int nb_sectors)
 {
+    BDRVVPCState *s = bs->opaque;
     int ret;
     int64_t offset;
+    int64_t sectors, sectors_per_block;
 
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 0);
 
+        sectors_per_block = s->block_size >> BDRV_SECTOR_BITS;
+        sectors = sectors_per_block - (sector_num % sectors_per_block);
+        if (sectors > nb_sectors) {
+            sectors = nb_sectors;
+        }
+
         if (offset == -1) {
-            memset(buf, 0, 512);
+            memset(buf, 0, sectors * BDRV_SECTOR_SIZE);
         } else {
-            ret = bdrv_pread(bs->file, offset, buf, 512);
-            if (ret != 512)
+            ret = bdrv_pread(bs->file, offset, buf,
+                sectors * BDRV_SECTOR_SIZE);
+            if (ret != sectors * BDRV_SECTOR_SIZE) {
                 return -1;
+            }
         }
 
-        nb_sectors--;
-        sector_num++;
-        buf += 512;
+        nb_sectors -= sectors;
+        sector_num += sectors;
+        buf += sectors * BDRV_SECTOR_SIZE;
     }
     return 0;
 }
@@ -395,25 +405,34 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num,
 static int vpc_write(BlockDriverState *bs, int64_t sector_num,
     const uint8_t *buf, int nb_sectors)
 {
+    BDRVVPCState *s = bs->opaque;
     int64_t offset;
+    int64_t sectors, sectors_per_block;
     int ret;
 
     while (nb_sectors > 0) {
         offset = get_sector_offset(bs, sector_num, 1);
 
+        sectors_per_block = s->block_size >> BDRV_SECTOR_BITS;
+        sectors = sectors_per_block - (sector_num % sectors_per_block);
+        if (sectors > nb_sectors) {
+            sectors = nb_sectors;
+        }
+
         if (offset == -1) {
             offset = alloc_block(bs, sector_num);
             if (offset < 0)
                 return -1;
         }
 
-        ret = bdrv_pwrite(bs->file, offset, buf, 512);
-        if (ret != 512)
+        ret = bdrv_pwrite(bs->file, offset, buf, sectors * BDRV_SECTOR_SIZE);
+        if (ret != sectors * BDRV_SECTOR_SIZE) {
             return -1;
+        }
 
-        nb_sectors--;
-        sector_num++;
-        buf += 512;
+        nb_sectors -= sectors;
+        sector_num += sectors;
+        buf += sectors * BDRV_SECTOR_SIZE;
     }
 
     return 0;