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    block: Make bdrv_is_allocated() byte-based · d6a644bb
    Eric Blake 提交于
    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 signature of the function to use int64_t *pnum 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
    on input and that *pnum is sector-aligned on return to the caller,
    but that can be relaxed when a later patch implements byte-based
    block status.  Therefore, this code adds usages like
    DIV_ROUND_UP(,BDRV_SECTOR_SIZE) to callers that still want aligned
    values, where the call might reasonbly give non-aligned results
    in the future; on the other hand, no rounding is needed for callers
    that should just continue to work with byte alignment.
    
    For the most part this patch is just the addition of scaling at the
    callers followed by inverse scaling at bdrv_is_allocated().  But
    some code, particularly bdrv_commit(), gets a lot simpler because it
    no longer has to mess with sectors; also, it is now possible to pass
    NULL if the caller does not care how much of the image is allocated
    beyond the initial offset.  Leave comments where we can further
    simplify once a later patch eliminates the need for sector-aligned
    requests through bdrv_is_allocated().
    
    For ease of review, bdrv_is_allocated_above() will be tackled
    separately.
    Signed-off-by: NEric Blake <eblake@redhat.com>
    Signed-off-by: NKevin Wolf <kwolf@redhat.com>
    d6a644bb
io.c 74.6 KB