[Qemu-devel] [PULL 09/18] block: Use 'detect-zeroes' option for 'blockdev-change-medium'

[Kevin Wolf <kwolf@redhat.com>]

Instead of modifying the new BDS after it has been opened, use the newly
supported 'detect-zeroes' option in bdrv_open_common() so that all
requirements are checked (detect-zeroes=unmap requires discard=unmap).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
 block/block-backend.c          | 9 ++++-----
 blockdev.c                     | 9 ++++++---
 include/sysemu/block-backend.h | 2 +-
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index f34bad5..639294b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1592,13 +1592,12 @@ void blk_update_root_state(BlockBackend *blk)
 }
 
 /*
- * Applies the information in the root state to the given BlockDriverState. This
- * does not include the flags which have to be specified for bdrv_open(), use
- * blk_get_open_flags_from_root_state() to inquire them.
+ * Returns the detect-zeroes setting to be used for bdrv_open() of a
+ * BlockDriverState which is supposed to inherit the root state.
  */
-void blk_apply_root_state(BlockBackend *blk, BlockDriverState *bs)
+bool blk_get_detect_zeroes_from_root_state(BlockBackend *blk)
 {
-    bs->detect_zeroes = blk->root_state.detect_zeroes;
+    return blk->root_state.detect_zeroes;
 }
 
 /*
diff --git a/blockdev.c b/blockdev.c
index 511260c..7b87bd8 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2546,6 +2546,7 @@ void qmp_blockdev_change_medium(bool has_device, const char *device,
     BlockBackend *blk;
     BlockDriverState *medium_bs = NULL;
     int bdrv_flags;
+    bool detect_zeroes;
     int rc;
     QDict *options = NULL;
     Error *err = NULL;
@@ -2585,8 +2586,12 @@ void qmp_blockdev_change_medium(bool has_device, const char *device,
         abort();
     }
 
+    options = qdict_new();
+    detect_zeroes = blk_get_detect_zeroes_from_root_state(blk);
+    qdict_put(options, "detect-zeroes",
+              qstring_from_str(detect_zeroes ? "on" : "off"));
+
     if (has_format) {
-        options = qdict_new();
         qdict_put(options, "driver", qstring_from_str(format));
     }
 
@@ -2623,8 +2628,6 @@ void qmp_blockdev_change_medium(bool has_device, const char *device,
         goto fail;
     }
 
-    blk_apply_root_state(blk, medium_bs);
-
     qmp_blockdev_close_tray(has_device, device, has_id, id, errp);
 
 fail:
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 24d1d85..a7993af 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -198,7 +198,7 @@ void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);
 BlockBackendRootState *blk_get_root_state(BlockBackend *blk);
 void blk_update_root_state(BlockBackend *blk);
-void blk_apply_root_state(BlockBackend *blk, BlockDriverState *bs);
+bool blk_get_detect_zeroes_from_root_state(BlockBackend *blk);
 int blk_get_open_flags_from_root_state(BlockBackend *blk);
 
 void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
-- 
1.8.3.1