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[Qemu-devel] [RFC v2 1/8] block: add bdrv_measure() API
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [RFC v2 1/8] block: add bdrv_measure() API |
Date: |
Wed, 15 Mar 2017 17:29:33 +0800 |
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 <address@hidden>
---
qapi/block-core.json | 19 +++++++++++++++++++
include/block/block.h | 4 ++++
include/block/block_int.h | 2 ++
block.c | 33 +++++++++++++++++++++++++++++++++
4 files changed, 58 insertions(+)
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 786b39e..673569d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -463,6 +463,25 @@
'*dirty-bitmaps': ['BlockDirtyInfo'] } }
##
+# @BlockMeasureInfo:
+#
+# Image size calculation information. This structure describes the size
+# requirements for creating a new image.
+#
+# @required-bytes: Amount of space required for image creation. This value is
+# the host file size including sparse file regions. A new 5
+# GB raw file therefore has a required size of 5 GB, not 0
+# bytes.
+#
+# @fully-allocated-bytes: Space required once data has been written to all
+# sectors
+#
+# Since: 2.10
+##
+{ 'struct': 'BlockMeasureInfo',
+ 'data': {'required-bytes': 'int', 'fully-allocated-bytes': '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 5149260..43c789f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -298,6 +298,10 @@ int bdrv_truncate(BdrvChild *child, int64_t offset);
int64_t bdrv_nb_sectors(BlockDriverState *bs);
int64_t bdrv_getlength(BlockDriverState *bs);
int64_t bdrv_get_allocated_file_size(BlockDriverState *bs);
+void bdrv_measure(BlockDriver *drv, QemuOpts *opts,
+ BlockDriverState *in_bs,
+ BlockMeasureInfo *info,
+ 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 6c699ac..45a7fbe 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -201,6 +201,8 @@ struct BlockDriver {
int64_t (*bdrv_getlength)(BlockDriverState *bs);
bool has_variable_length;
int64_t (*bdrv_get_allocated_file_size)(BlockDriverState *bs);
+ void (*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
+ BlockMeasureInfo *info, 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 cb57370..532a4d1 100644
--- a/block.c
+++ b/block.c
@@ -3260,6 +3260,39 @@ int64_t bdrv_get_allocated_file_size(BlockDriverState
*bs)
return -ENOTSUP;
}
+/*
+ * bdrv_measure:
+ * @drv: Format driver
+ * @opts: Creation options
+ * @in_bs: Existing image containing data for new image (may be NULL)
+ * @info: Result object
+ * @errp: Error object
+ *
+ * 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 are 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.
+ */
+void bdrv_measure(BlockDriver *drv, QemuOpts *opts,
+ BlockDriverState *in_bs, BlockMeasureInfo *info,
+ Error **errp)
+{
+ if (!drv->bdrv_measure) {
+ error_setg(errp, "Block driver '%s' does not support size measurement",
+ drv->format_name);
+ return;
+ }
+
+ drv->bdrv_measure(opts, in_bs, info, errp);
+}
+
/**
* Return number of sectors on success, -errno on error.
*/
--
2.9.3