[Qemu-devel] [PATCH 1/2] migration/block: Convert load to BlockBackend

[Kevin Wolf <kwolf@redhat.com>]

This converts the loading part of block migration to use BlockBackend
interfaces rather than accessing the BlockDriverState directly.

Note that this takes a lazy shortcut. We should really use a separate
BlockBackend that is configured for the migration rather than for the
guest (e.g. writethrough caching is unnecessary) and holds its own
reference to the BlockDriverState, but the impact isn't that big and we
didn't have a separate migration reference before either, so it must be
good enough, I guess...

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 migration/block.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/migration/block.c b/migration/block.c
index e0628d1..30af182 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -827,8 +827,7 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
     int len, flags;
     char device_name[256];
     int64_t addr;
-    BlockDriverState *bs, *bs_prev = NULL;
-    BlockBackend *blk;
+    BlockBackend *blk, *blk_prev = NULL;;
     Error *local_err = NULL;
     uint8_t *buf;
     int64_t total_sectors = 0;
@@ -853,23 +852,17 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
                         device_name);
                 return -EINVAL;
             }
-            bs = blk_bs(blk);
-            if (!bs) {
-                fprintf(stderr, "Block device %s has no medium\n",
-                        device_name);
-                return -EINVAL;
-            }
 
-            if (bs != bs_prev) {
-                bs_prev = bs;
-                total_sectors = bdrv_nb_sectors(bs);
+            if (blk != blk_prev) {
+                blk_prev = blk;
+                total_sectors = blk_nb_sectors(blk);
                 if (total_sectors <= 0) {
                     error_report("Error getting length of block device %s",
                                  device_name);
                     return -EINVAL;
                 }
 
-                bdrv_invalidate_cache(bs, &local_err);
+                blk_invalidate_cache(blk, &local_err);
                 if (local_err) {
                     error_report_err(local_err);
                     return -EINVAL;
@@ -883,12 +876,14 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
             }
 
             if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
-                ret = bdrv_write_zeroes(bs, addr, nr_sectors,
+                ret = blk_pwrite_zeroes(blk, addr * BDRV_SECTOR_SIZE,
+                                        nr_sectors * BDRV_SECTOR_SIZE,
                                         BDRV_REQ_MAY_UNMAP);
             } else {
                 buf = g_malloc(BLOCK_SIZE);
                 qemu_get_buffer(f, buf, BLOCK_SIZE);
-                ret = bdrv_write(bs, addr, buf, nr_sectors);
+                ret = blk_pwrite(blk, addr * BDRV_SECTOR_SIZE, buf,
+                                 nr_sectors * BDRV_SECTOR_SIZE, 0);
                 g_free(buf);
             }
 
-- 
1.8.3.1