From: Stefan Hajnoczi <stefa...@redhat.com>
bdrv_measure() provides a conservative maximum for the size of a new
image. This information is handy if storage needs to be allocated (e.g.
a SAN or an LVM volume) ahead of time.
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Alberto Garcia <be...@igalia.com>
Message-id: 20170705125738.8777-2-stefa...@redhat.com
Signed-off-by: Max Reitz <mre...@redhat.com>
---
qapi/block-core.json | 25 +++++++++++++++++++++++++
include/block/block.h | 2 ++
include/block/block_int.h | 2 ++
block.c | 35 +++++++++++++++++++++++++++++++++++
4 files changed, 64 insertions(+)
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 4bf11e8..c437aa5 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -488,6 +488,31 @@
'*dirty-bitmaps': ['BlockDirtyInfo'] } }
##
+# @BlockMeasureInfo:
+#
+# Image file size calculation information. This structure describes the size
+# requirements for creating a new image file.
+#
+# The size requirements depend on the new image file format. File size always
+# equals virtual disk size for the 'raw' format, even for sparse POSIX files.
+# Compact formats such as 'qcow2' represent unallocated and zero regions
+# efficiently so file size may be smaller than virtual disk size.
+#
+# The values are upper bounds that are guaranteed to fit the new image file.
+# Subsequent modification, such as internal snapshot or bitmap creation, may
+# require additional space and is not covered here.
+#
+# @required: Size required for a new image file, in bytes.
+#
+# @fully-allocated: Image file size, in bytes, once data has been written
+# to all sectors.
+#
+# Since: 2.10
+##
+{ 'struct': 'BlockMeasureInfo',
+ 'data': {'required': 'int', 'fully-allocated': 'int'} }
+
+##
# @query-block:
#
# Get a list of BlockInfo for all virtual block devices.
diff --git a/include/block/block.h b/include/block/block.h
index f0fdbe8..96edc85 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -306,6 +306,8 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, Error
**errp);
int64_t bdrv_nb_sectors(BlockDriverState *bs);
int64_t bdrv_getlength(BlockDriverState *bs);
int64_t bdrv_get_allocated_file_size(BlockDriverState *bs);
+BlockMeasureInfo *bdrv_measure(BlockDriver *drv, QemuOpts *opts,
+ BlockDriverState *in_bs, Error **errp);
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
void bdrv_refresh_limits(BlockDriverState *bs, Error **errp);
int bdrv_commit(BlockDriverState *bs);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 58d4ffd..d0cd8a3 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -209,6 +209,8 @@ struct BlockDriver {
int64_t (*bdrv_getlength)(BlockDriverState *bs);
bool has_variable_length;
int64_t (*bdrv_get_allocated_file_size)(BlockDriverState *bs);
+ BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
+ Error **errp);
int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov);
diff --git a/block.c b/block.c
index 913bb43..162e9d9 100644
--- a/block.c
+++ b/block.c
@@ -3463,6 +3463,41 @@ int64_t bdrv_get_allocated_file_size(BlockDriverState
*bs)
return -ENOTSUP;
}
+/*
+ * bdrv_measure:
+ * @drv: Format driver
+ * @opts: Creation options for new image
+ * @in_bs: Existing image containing data for new image (may be NULL)
+ * @errp: Error object
+ * Returns: A #BlockMeasureInfo (free using qapi_free_BlockMeasureInfo())
+ * or NULL on error
+ *
+ * Calculate file size required to create a new image.
+ *
+ * If @in_bs is given then space for allocated clusters and zero clusters
+ * from that image are included in the calculation. If @opts contains a
+ * backing file that is shared by @in_bs then backing clusters may be omitted
+ * from the calculation.
+ *
+ * If @in_bs is NULL then the calculation includes no allocated clusters
+ * unless a preallocation option is given in @opts.
+ *
+ * Note that @in_bs may use a different BlockDriver from @drv.
+ *
+ * If an error occurs the @errp pointer is set.
+ */
+BlockMeasureInfo *bdrv_measure(BlockDriver *drv, QemuOpts *opts,
+ BlockDriverState *in_bs, Error **errp)
+{
+ if (!drv->bdrv_measure) {
+ error_setg(errp, "Block driver '%s' does not support size measurement",
+ drv->format_name);
+ return NULL;
+ }
+
+ return drv->bdrv_measure(opts, in_bs, errp);
+}
+
/**
* Return number of sectors on success, -errno on error.
*/
--
2.9.4
