diff --git a/block-migration.c b/block-migration.c
index 37e41ab..5aff5a7 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -17,11 +17,7 @@
 #include "block-migration.h"
 #include <assert.h>
 
-#define SECTOR_BITS 9
-#define SECTOR_SIZE (1 << SECTOR_BITS)
-#define SECTOR_MASK ~(SECTOR_SIZE - 1);
-
-#define BLOCK_SIZE (block_mig_state->sectors_per_block << SECTOR_BITS)
+#define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
 
 #define BLK_MIG_FLAG_DEVICE_BLOCK       0x01
 #define BLK_MIG_FLAG_EOS                0x02
@@ -69,7 +65,6 @@ typedef struct BlkMigState {
     int no_dirty;
     QEMUFile *load_file;
     BlkMigDevState *bmds_first;
-    int sectors_per_block;
     BlkMigBlock *first_blk;
     BlkMigBlock *last_blk;
     int submitted;
@@ -111,7 +106,7 @@ static int mig_read_device_bulk(QEMUFile *f, BlkMigDevState *bms)
     blk->buf = qemu_malloc(BLOCK_SIZE);
 
     cur_sector = bms->cur_sector;
-    total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;
+    total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
 
     if (bms->shared_base) {
         while (cur_sector < bms->total_sectors &&
@@ -132,15 +127,15 @@ static int mig_read_device_bulk(QEMUFile *f, BlkMigDevState *bms)
         printf("Completed %" PRId64 " %%\r", cur_sector * 100 / total_sectors);
         fflush(stdout);
         block_mig_state->print_completion +=
-            (block_mig_state->sectors_per_block * 10000);
+            (BDRV_SECTORS_PER_DIRTY_CHUNK * 10000);
     }
 
-    /* we going to transfder BLOCK_SIZE any way even if it is not allocated */
-    nr_sectors = block_mig_state->sectors_per_block;
+    /* we are going to transfer a full block even if it is not allocated */
+    nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
 
-    cur_sector &= ~((int64_t)block_mig_state->sectors_per_block -1);
+    cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);
 
-    if (total_sectors - cur_sector < block_mig_state->sectors_per_block) {
+    if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
         nr_sectors = (total_sectors - cur_sector);
     }
 
@@ -150,7 +145,7 @@ static int mig_read_device_bulk(QEMUFile *f, BlkMigDevState *bms)
     blk->next = NULL;
 
     blk->iov.iov_base = blk->buf;
-    blk->iov.iov_len = nr_sectors * SECTOR_SIZE;
+    blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
 
     blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
@@ -198,15 +193,15 @@ static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
         printf("Completed %" PRId64 " %%\r", cur_sector * 100 / total_sectors);
         fflush(stdout);
         block_mig_state->print_completion +=
-            (block_mig_state->sectors_per_block * 10000);
+            (BDRV_SECTORS_PER_DIRTY_CHUNK * 10000);
     }
 
-    cur_sector &= ~((int64_t)block_mig_state->sectors_per_block -1);
+    cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);
 
-    /* we going to transfer BLOCK_SIZE any way even if it is not allocated */
-    nr_sectors = block_mig_state->sectors_per_block;
+    /* we are going to transfer a full block even if it is not allocated */
+    nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
 
-    if (total_sectors - cur_sector < block_mig_state->sectors_per_block) {
+    if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
         nr_sectors = (total_sectors - cur_sector);
     }
 
@@ -217,7 +212,8 @@ static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
     bdrv_reset_dirty(bs, cur_sector, nr_sectors);
 
     /* sector number and flags */
-    qemu_put_be64(f, (cur_sector << SECTOR_BITS) | BLK_MIG_FLAG_DEVICE_BLOCK);
+    qemu_put_be64(f, (cur_sector << BDRV_SECTOR_BITS)
+                     | BLK_MIG_FLAG_DEVICE_BLOCK);
 
     /* device name */
     len = strlen(bs->device_name);
@@ -226,7 +222,7 @@ static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds)
 
     qemu_put_buffer(f, tmp_buf, BLOCK_SIZE);
 
-    bmds->cur_sector = cur_sector + block_mig_state->sectors_per_block;
+    bmds->cur_sector = cur_sector + BDRV_SECTORS_PER_DIRTY_CHUNK;
 
     qemu_free(tmp_buf);
 
@@ -238,7 +234,8 @@ static void send_blk(QEMUFile *f, BlkMigBlock * blk)
     int len;
 
     /* sector number and flags */
-    qemu_put_be64(f, (blk->sector << SECTOR_BITS) | BLK_MIG_FLAG_DEVICE_BLOCK);
+    qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
+                     | BLK_MIG_FLAG_DEVICE_BLOCK);
 
     /* device name */
     len = strlen(blk->bmds->bs->device_name);
@@ -270,7 +267,7 @@ static void init_blk_migration(QEMUFile *f)
             bmds = qemu_mallocz(sizeof(BlkMigDevState));
             bmds->bs = bs;
             bmds->bulk_completed = 0;
-            bmds->total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;
+            bmds->total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
             bmds->shared_base = block_mig_state->shared_base;
 
             if (bmds->shared_base) {
@@ -290,8 +287,6 @@ static void init_blk_migration(QEMUFile *f)
             blk_mig_save_dev_info(f, bmds);
         }
     }
-
-    block_mig_state->sectors_per_block = bdrv_get_sectors_per_chunk();
 }
 
 static int blk_mig_save_bulked_block(QEMUFile *f, int is_async)
@@ -334,12 +329,12 @@ static void blk_mig_save_dirty_blocks(QEMUFile *f)
         for (sector = 0; sector < bmds->cur_sector;) {
             if (bdrv_get_dirty(bmds->bs, sector)) {
                 if (bdrv_read(bmds->bs, sector, buf,
-                              block_mig_state->sectors_per_block) < 0) {
+                              BDRV_SECTORS_PER_DIRTY_CHUNK) < 0) {
                     /* FIXME: add error handling */
                 }
 
                 /* sector number and flags */
-                qemu_put_be64(f, (sector << SECTOR_BITS)
+                qemu_put_be64(f, (sector << BDRV_SECTOR_BITS)
                                  | BLK_MIG_FLAG_DEVICE_BLOCK);
 
                 /* device name */
@@ -347,14 +342,12 @@ static void blk_mig_save_dirty_blocks(QEMUFile *f)
                 qemu_put_byte(f, len);
                 qemu_put_buffer(f, (uint8_t *)bmds->bs->device_name, len);
 
-                qemu_put_buffer(f, buf,
-                                (block_mig_state->sectors_per_block *
-                                 SECTOR_SIZE));
+                qemu_put_buffer(f, buf, BLOCK_SIZE);
 
                 bdrv_reset_dirty(bmds->bs, sector,
-                                 block_mig_state->sectors_per_block);
+                                 BDRV_SECTORS_PER_DIRTY_CHUNK);
             }
-            sector += block_mig_state->sectors_per_block;
+            sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
         }
     }
 }
@@ -465,14 +458,13 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
     BlockDriverState *bs;
     uint8_t *buf;
 
-    block_mig_state->sectors_per_block = bdrv_get_sectors_per_chunk();
     buf = qemu_malloc(BLOCK_SIZE);
 
     do {
         addr = qemu_get_be64(f);
 
-        flags = addr & ~SECTOR_MASK;
-        addr &= SECTOR_MASK;
+        flags = addr & ~BDRV_SECTOR_MASK;
+        addr >>= BDRV_SECTOR_BITS;
 
         if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
             /* get device name */
@@ -485,8 +477,7 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
 
             qemu_get_buffer(f, buf, BLOCK_SIZE);
             if (bs != NULL) {
-                bdrv_write(bs, (addr >> SECTOR_BITS),
-                           buf, block_mig_state->sectors_per_block);
+                bdrv_write(bs, addr, buf, BDRV_SECTORS_PER_DIRTY_CHUNK);
             } else {
                 printf("Error unknown block device %s\n", device_name);
                 /* FIXME: add error handling */
diff --git a/block.c b/block.c
index 75ea223..9ce6d8a 100644
--- a/block.c
+++ b/block.c
@@ -41,10 +41,6 @@
 #include <windows.h>
 #endif
 
-#define SECTOR_BITS 9
-#define SECTOR_SIZE (1 << SECTOR_BITS)
-#define SECTORS_PER_DIRTY_CHUNK 8
-
 static BlockDriverAIOCB *bdrv_aio_readv_em(BlockDriverState *bs,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque);
@@ -386,7 +382,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
             bdrv_delete(bs1);
             return ret;
         }
-        total_size = bdrv_getlength(bs1) >> SECTOR_BITS;
+        total_size = bdrv_getlength(bs1) >> BDRV_SECTOR_BITS;
 
         if (bs1->drv && bs1->drv->protocol_name)
             is_protocol = 1;
@@ -473,7 +469,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
         return ret;
     }
     if (drv->bdrv_getlength) {
-        bs->total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;
+        bs->total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
     }
 #ifndef _WIN32
     if (bs->is_temporary) {
@@ -576,7 +572,7 @@ int bdrv_commit(BlockDriverState *bs)
 	return -ENOTSUP;
     }
 
-    total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;
+    total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
     for (i = 0; i < total_sectors;) {
         if (drv->bdrv_is_allocated(bs, i, 65536, &n)) {
             for(j = 0; j < n; j++) {
@@ -647,8 +643,8 @@ static void set_dirty_bitmap(BlockDriverState *bs, int64_t sector_num,
 {
     int64_t start, end;
 
-    start = sector_num / SECTORS_PER_DIRTY_CHUNK;
-    end = (sector_num + nb_sectors) / SECTORS_PER_DIRTY_CHUNK;
+    start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
+    end = (sector_num + nb_sectors) / BDRV_SECTORS_PER_DIRTY_CHUNK;
 
     for (; start <= end; start++) {
         bs->dirty_bitmap[start] = dirty;
@@ -682,20 +678,20 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
 int bdrv_pread(BlockDriverState *bs, int64_t offset,
                void *buf, int count1)
 {
-    uint8_t tmp_buf[SECTOR_SIZE];
+    uint8_t tmp_buf[BDRV_SECTOR_SIZE];
     int len, nb_sectors, count;
     int64_t sector_num;
 
     count = count1;
     /* first read to align to sector start */
-    len = (SECTOR_SIZE - offset) & (SECTOR_SIZE - 1);
+    len = (BDRV_SECTOR_SIZE - offset) & (BDRV_SECTOR_SIZE - 1);
     if (len > count)
         len = count;
-    sector_num = offset >> SECTOR_BITS;
+    sector_num = offset >> BDRV_SECTOR_BITS;
     if (len > 0) {
         if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)
             return -EIO;
-        memcpy(buf, tmp_buf + (offset & (SECTOR_SIZE - 1)), len);
+        memcpy(buf, tmp_buf + (offset & (BDRV_SECTOR_SIZE - 1)), len);
         count -= len;
         if (count == 0)
             return count1;
@@ -704,12 +700,12 @@ int bdrv_pread(BlockDriverState *bs, int64_t offset,
     }
 
     /* read the sectors "in place" */
-    nb_sectors = count >> SECTOR_BITS;
+    nb_sectors = count >> BDRV_SECTOR_BITS;
     if (nb_sectors > 0) {
         if (bdrv_read(bs, sector_num, buf, nb_sectors) < 0)
             return -EIO;
         sector_num += nb_sectors;
-        len = nb_sectors << SECTOR_BITS;
+        len = nb_sectors << BDRV_SECTOR_BITS;
         buf += len;
         count -= len;
     }
@@ -726,20 +722,20 @@ int bdrv_pread(BlockDriverState *bs, int64_t offset,
 int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
                 const void *buf, int count1)
 {
-    uint8_t tmp_buf[SECTOR_SIZE];
+    uint8_t tmp_buf[BDRV_SECTOR_SIZE];
     int len, nb_sectors, count;
     int64_t sector_num;
 
     count = count1;
     /* first write to align to sector start */
-    len = (SECTOR_SIZE - offset) & (SECTOR_SIZE - 1);
+    len = (BDRV_SECTOR_SIZE - offset) & (BDRV_SECTOR_SIZE - 1);
     if (len > count)
         len = count;
-    sector_num = offset >> SECTOR_BITS;
+    sector_num = offset >> BDRV_SECTOR_BITS;
     if (len > 0) {
         if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)
             return -EIO;
-        memcpy(tmp_buf + (offset & (SECTOR_SIZE - 1)), buf, len);
+        memcpy(tmp_buf + (offset & (BDRV_SECTOR_SIZE - 1)), buf, len);
         if (bdrv_write(bs, sector_num, tmp_buf, 1) < 0)
             return -EIO;
         count -= len;
@@ -750,12 +746,12 @@ int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
     }
 
     /* write the sectors "in place" */
-    nb_sectors = count >> SECTOR_BITS;
+    nb_sectors = count >> BDRV_SECTOR_BITS;
     if (nb_sectors > 0) {
         if (bdrv_write(bs, sector_num, buf, nb_sectors) < 0)
             return -EIO;
         sector_num += nb_sectors;
-        len = nb_sectors << SECTOR_BITS;
+        len = nb_sectors << BDRV_SECTOR_BITS;
         buf += len;
         count -= len;
     }
@@ -796,7 +792,7 @@ int64_t bdrv_getlength(BlockDriverState *bs)
         return -ENOMEDIUM;
     if (!drv->bdrv_getlength) {
         /* legacy mode */
-        return bs->total_sectors * SECTOR_SIZE;
+        return bs->total_sectors * BDRV_SECTOR_SIZE;
     }
     return drv->bdrv_getlength(bs);
 }
@@ -809,7 +805,7 @@ void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
     if (length < 0)
         length = 0;
     else
-        length = length >> SECTOR_BITS;
+        length = length >> BDRV_SECTOR_BITS;
     *nb_sectors_ptr = length;
 }
 
@@ -1402,7 +1398,7 @@ BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num,
 
     if (ret) {
 	/* Update stats even though technically transfer has not happened. */
-	bs->rd_bytes += (unsigned) nb_sectors * SECTOR_SIZE;
+	bs->rd_bytes += (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
 	bs->rd_ops ++;
     }
 
@@ -1432,7 +1428,7 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
 
     if (ret) {
 	/* Update stats even though technically transfer has not happened. */
-	bs->wr_bytes += (unsigned) nb_sectors * SECTOR_SIZE;
+	bs->wr_bytes += (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
 	bs->wr_ops ++;
     }
 
@@ -1973,8 +1969,8 @@ void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable)
             int64_t i;
             uint8_t test;
 
-            bitmap_size = (bdrv_getlength(bs) >> SECTOR_BITS);
-            bitmap_size /= SECTORS_PER_DIRTY_CHUNK;
+            bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
+            bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK;
             bitmap_size++;
 
             bs->dirty_bitmap = qemu_mallocz(bitmap_size);
@@ -1992,10 +1988,10 @@ void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable)
 
 int bdrv_get_dirty(BlockDriverState *bs, int64_t sector)
 {
-    int64_t chunk = sector / (int64_t)SECTORS_PER_DIRTY_CHUNK;
+    int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
 
     if (bs->dirty_bitmap != NULL &&
-        (sector << SECTOR_BITS) <= bdrv_getlength(bs)) {
+        (sector << BDRV_SECTOR_BITS) <= bdrv_getlength(bs)) {
         return bs->dirty_bitmap[chunk];
     } else {
         return 0;
@@ -2007,9 +2003,3 @@ void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
 {
     set_dirty_bitmap(bs, cur_sector, nr_sectors, 0);
 }
-
-int bdrv_get_sectors_per_chunk(void)
-{
-    /* size must be 2^x */
-    return SECTORS_PER_DIRTY_CHUNK;
-}
diff --git a/block.h b/block.h
index 85d231d..3513712 100644
--- a/block.h
+++ b/block.h
@@ -41,6 +41,10 @@ typedef struct QEMUSnapshotInfo {
 
 #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_CACHE_WB)
 
+#define BDRV_SECTOR_BITS   9
+#define BDRV_SECTOR_SIZE   (1 << BDRV_SECTOR_BITS)
+#define BDRV_SECTOR_MASK   ~(BDRV_SECTOR_SIZE - 1);
+
 void bdrv_info(Monitor *mon);
 void bdrv_info_stats(Monitor *mon);
 
@@ -188,9 +192,10 @@ int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
 int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
                       int64_t pos, int size);
 
+#define BDRV_SECTORS_PER_DIRTY_CHUNK 8
+
 void bdrv_set_dirty_tracking(BlockDriverState *bs, int enable);
 int bdrv_get_dirty(BlockDriverState *bs, int64_t sector);
 void bdrv_reset_dirty(BlockDriverState *bs, int64_t cur_sector,
                       int nr_sectors);
-int bdrv_get_sectors_per_chunk(void);
 #endif
