block/parallels: switch to bdrv_read

block/parallels: switch to bdrv_read

Switch the .bdrv_read method implementation from using bdrv_pread() to
bdrv_read() on the underlying file, since the latter is subject to i/o
throttling while the former is not.

Besides, since bdrv_read() operates in sectors rather than bytes, adjust
the helper functions to do so too.

Signed-off-by: Roman Kagan <[email protected]>
Reviewed-by: Denis V. Lunev <[email protected]>
Signed-off-by: Denis V. Lunev <[email protected]>
Message-id: 1430207220[email protected]
CC: Kevin Wolf <[email protected]>
CC: Stefan Hajnoczi <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>