Am 12.10.2017 um 05:47 hat Eric Blake geschrieben: > 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_above() > to bdrv_block_status_above() ensures that the compiler enforces that > all callers are updated. Likewise, since it a byte interface allows > an offset mapping that might not be sector aligned, split the mapping > out of the return value and into a pass-by-reference parameter. For > now, the io.c layer still assert()s that all uses are sector-aligned, > but that can be relaxed when a later patch implements byte-based > block status in the drivers. > > For the most part this patch is just the addition of scaling at the > callers followed by inverse scaling at bdrv_block_status(), plus > updates for the new split return interface. But some code, > particularly bdrv_block_status(), gets a lot simpler because it no > longer has to mess with sectors. Likewise, mirror code no longer > computes s->granularity >> BDRV_SECTOR_BITS, and can therefore drop > an assertion about alignment because the loop no longer depends on > alignment (never mind that we don't really have a driver that > reports sub-sector alignments, so it's not really possible to test > the effect of sub-sector mirroring). Fix a neighboring assertion to > use is_power_of_2 while there. > > For ease of review, bdrv_get_block_status() was tackled separately. > > Signed-off-by: Eric Blake <ebl...@redhat.com>
> int bdrv_block_status(BlockDriverState *bs, int64_t offset, int64_t bytes, > int64_t *pnum, int64_t *map, BlockDriverState **file) > { > - int64_t ret; > - int n; > - > - assert(QEMU_IS_ALIGNED(offset | bytes, BDRV_SECTOR_SIZE)); > - assert(pnum); > - /* > - * The contract allows us to return pnum smaller than bytes, even > - * if the next query would see the same status; we truncate the > - * request to avoid overflowing the driver's 32-bit interface. > - */ > - bytes = MIN(bytes, BDRV_REQUEST_MAX_BYTES); Is the limitation to BDRV_REQUEST_MAX_BYTES going away without being replaced by a new one in bdrv_co_block_status()? What protects us now from 32-bit truncation? Kevin