block: add bdrv_measure() API

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 <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20170705125738.8777-2-stefanha@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2017-07-05 13:57:30 +01:00 committed by Max Reitz
parent b43671f80c
commit 90880ff107
4 changed files with 64 additions and 0 deletions

35
block.c
View file

@ -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.
*/

View file

@ -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);

View file

@ -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);

View file

@ -487,6 +487,31 @@
'*tray_open': 'bool', '*io-status': 'BlockDeviceIoStatus',
'*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:
#