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> --- qapi/block-core.json | 25 +++++++++++++++++++++++++ include/block/block.h | 4 ++++ include/block/block_int.h | 2 ++ block.c | 35 +++++++++++++++++++++++++++++++++++ 4 files changed, 66 insertions(+) diff --git a/qapi/block-core.json b/qapi/block-core.json index 0f132fc..42fb90e 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -463,6 +463,31 @@ '*dirty-bitmaps': ['BlockDirtyInfo'] } } ## +# @BlockMeasureInfo: +# +# Image 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. 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 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 59400bd..5099a58 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 6e906ec..a191b82 100644 --- a/block.c +++ b/block.c @@ -3266,6 +3266,41 @@ 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) + * @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. + * + * If an error occurs the @errp pointer is set. + */ +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