Re: [Qemu-devel] [PATCH v2 08/15] block: Convert bdrv_get_block_status() to bytes

[Fam Zheng <famz@redhat.com>]

On Mon, 07/03 17:14, Eric Blake wrote:
> We are gradually moving away from sector-based interfaces, towards
> byte-based.  In the common case, allocation is unlikely to ever use
> values that are not naturally sector-aligned, but it is possible
> that byte-based values will let us be more precise about allocation
> at the end of an unaligned file that can do byte-based access.
> 
> Changing the name of the function from bdrv_get_block_status() to
> bdrv_block_status() ensures that the compiler enforces that all
> callers are updated.  For now, the io.c layer still assert()s that
> all callers are sector-aligned, but that can be relaxed when a later
> patch implements byte-based block status in the drivers.
> 
> Note that we have an inherent limitation in the BDRV_BLOCK_* return
> values: BDRV_BLOCK_OFFSET_VALID can only return the start of a
> sector, even if we later relax the interface to query for the status
> starting at an intermediate byte; document the obvious interpretation
> that valid offsets are always sector-relative.
> 
> Therefore, for the most part this patch is just the addition of scaling
> at the callers followed by inverse scaling at bdrv_block_status().  But
> some code, particularly bdrv_is_allocated(), gets a lot simpler because
> it no longer has to mess with sectors.
> 
> For ease of review, bdrv_get_block_status_above() will be tackled
> separately.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> 

Reviewed-by: Fam Zheng <famz@redhat.com>