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block: New bdrv_nb_sectors() 

A call to retrieve the image size converts between bytes and sectors
several times:

* BlockDriver method bdrv_getlength() returns bytes.

* refresh_total_sectors() converts to sectors, rounding up, and stores
  in total_sectors.

* bdrv_getlength() converts total_sectors back to bytes (now rounded
  up to a multiple of the sector size).

* Callers wanting sectors rather bytes convert it right back.
  Example: bdrv_get_geometry().

bdrv_nb_sectors() provides a way to omit the last two conversions.
It's exactly bdrv_getlength() with the conversion to bytes omitted.
It's functionally like bdrv_get_geometry() without its odd error
handling.

Reimplement bdrv_getlength() and bdrv_get_geometry() on top of
bdrv_nb_sectors().

The next patches will convert some users of bdrv_getlength() to
bdrv_nb_sectors().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Markus Armbruster 2014-06-26 13:23:17 +02:00 committed by Kevin Wolf
parent 69f87f7130
commit 65a9bb25d6
2 changed files with 20 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
block.c
View File

@ -701,6 +701,7 @@ static int find_image_format(BlockDriverState *bs, const char *filename,
/**
* Set the current 'total_sectors' value
* Return 0 on success, -errno on error.
*/
static int refresh_total_sectors(BlockDriverState *bs, int64_t hint)
{
@ -3536,11 +3537,12 @@ int64_t bdrv_get_allocated_file_size(BlockDriverState *bs)
}
/**
* Length of a file in bytes. Return < 0 if error or unknown.
* Return number of sectors on success, -errno on error.
*/
int64_t bdrv_getlength(BlockDriverState *bs)
int64_t bdrv_nb_sectors(BlockDriverState *bs)
{
BlockDriver *drv = bs->drv;
if (!drv)
return -ENOMEDIUM;
@ -3550,19 +3552,26 @@ int64_t bdrv_getlength(BlockDriverState *bs)
return ret;
}
}
return bs->total_sectors * BDRV_SECTOR_SIZE;
return bs->total_sectors;
}
/**
* Return length in bytes on success, -errno on error.
* The length is always a multiple of BDRV_SECTOR_SIZE.
*/
int64_t bdrv_getlength(BlockDriverState *bs)
{
int64_t ret = bdrv_nb_sectors(bs);
return ret < 0 ? ret : ret * BDRV_SECTOR_SIZE;
}
/* return 0 as number of sectors if no device present or error */
void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
{
int64_t length;
length = bdrv_getlength(bs);
if (length < 0)
length = 0;
else
length = length >> BDRV_SECTOR_BITS;
*nb_sectors_ptr = length;
int64_t nb_sectors = bdrv_nb_sectors(bs);
*nb_sectors_ptr = nb_sectors < 0 ? 0 : nb_sectors;
}
void bdrv_set_on_error(BlockDriverState *bs, BlockdevOnError on_read_error,

1
include/block/block.h
View File

@ -275,6 +275,7 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
const char *backing_file);
int bdrv_get_backing_file_depth(BlockDriverState *bs);
int bdrv_truncate(BlockDriverState *bs, 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_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);