[Qemu-devel] [RFC 1/3] block: Add ImageRotationalInfo

[Max Reitz <mreitz@redhat.com>]

This enum indicates whether a file is stored on a rotating disk or a
solid-state drive.  Drivers report it via the .bdrv_get_info() callback,
and if they do not, the global bdrv_get_info() implementation
automatically takes it from bs->file or bs->backing, if available.

On the QAPI side, we report the value as part of the ImageInfo
structure.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 qapi/block-core.json  | 19 ++++++++++++++++++-
 include/block/block.h |  7 +++++++
 block.c               | 20 +++++++++++++++++++-
 block/qapi.c          |  3 +++
 4 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 3e4042be7f..80b9f2a69c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -130,6 +130,20 @@
       'luks': 'QCryptoBlockInfoLUKS'
   } }
 
+##
+# @ImageRotationalInfo:
+#
+# Indicates whether an image is stored on a rotating disk or not.
+#
+# @solid-state: Image is stored on a solid-state drive
+#
+# @rotating:    Image is stored on a rotating disk
+#
+# Since: 4.1
+##
+{ 'enum': 'ImageRotationalInfo',
+  'data': [ 'solid-state', 'rotating' ] }
+
 ##
 # @ImageInfo:
 #
@@ -161,6 +175,9 @@
 #
 # @backing-image: info of the backing image (since 1.6)
 #
+# @rotational: indicates whether the image is stored on a rotating
+#              disk or not (since 4.1)
+#
 # @format-specific: structure supplying additional format-specific
 # information (since 1.7)
 #
@@ -173,7 +190,7 @@
            '*cluster-size': 'int', '*encrypted': 'bool', '*compressed': 'bool',
            '*backing-filename': 'str', '*full-backing-filename': 'str',
            '*backing-filename-format': 'str', '*snapshots': ['SnapshotInfo'],
-           '*backing-image': 'ImageInfo',
+           '*backing-image': 'ImageInfo', '*rotational': 'ImageRotationalInfo',
            '*format-specific': 'ImageInfoSpecific' } }
 
 ##
diff --git a/include/block/block.h b/include/block/block.h
index 531cf595cf..dc0f8a4671 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -31,6 +31,13 @@ typedef struct BlockDriverInfo {
      * True if this block driver only supports compressed writes
      */
     bool needs_compressed_writes;
+
+    /*
+     * Indicates whether this image file is stored on a rotating disk
+     * or a solid-state drive.
+     */
+    bool has_rotational_info;
+    ImageRotationalInfo rotational_info;
 } BlockDriverInfo;
 
 typedef struct BlockFragInfo {
diff --git a/block.c b/block.c
index 4c3902508d..e6b2d6d23b 100644
--- a/block.c
+++ b/block.c
@@ -4950,6 +4950,8 @@ void bdrv_get_backing_filename(BlockDriverState *bs,
 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 {
     BlockDriver *drv = bs->drv;
+    int ret;
+
     /* if bs->drv == NULL, bs is closed, so there's nothing to do here */
     if (!drv) {
         return -ENOMEDIUM;
@@ -4960,8 +4962,24 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
         }
         return -ENOTSUP;
     }
+
     memset(bdi, 0, sizeof(*bdi));
-    return drv->bdrv_get_info(bs, bdi);
+    ret = drv->bdrv_get_info(bs, bdi);
+    if (ret < 0) {
+        return ret;
+    }
+
+    if (!bdi->has_rotational_info && (bs->file || bs->backing)) {
+        BlockDriverState *child = bs->file ? bs->file->bs : bs->backing->bs;
+        BlockDriverInfo child_bdi;
+
+        if (bdrv_get_info(child, &child_bdi) >= 0) {
+            bdi->rotational_info = child_bdi.rotational_info;
+            bdi->has_rotational_info = child_bdi.has_rotational_info;
+        }
+    }
+
+    return 0;
 }
 
 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs,
diff --git a/block/qapi.c b/block/qapi.c
index 0c13c86f4e..48ebfbdcc1 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -286,6 +286,9 @@ void bdrv_query_image_info(BlockDriverState *bs,
         }
         info->dirty_flag = bdi.is_dirty;
         info->has_dirty_flag = true;
+
+        info->rotational = bdi.rotational_info;
+        info->has_rotational = bdi.has_rotational_info;
     }
     info->format_specific = bdrv_get_specific_info(bs, &err);
     if (err) {
-- 
2.21.0