Am 18.02.2015 um 21:57 schrieb Peter Lieven: > This implements bdrv_co_get_block_status() for VHD images. This can > significantly speed up qemu-img convert operation because only with this > function implemented sparseness can be considered. (Before, converting a > 1 TB empty image took several minutes for me, now it's instantaneous.) > > Signed-off-by: Kevin Wolf <[email protected]> > --- > block/vpc.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 48 insertions(+), 2 deletions(-) > > diff --git a/block/vpc.c b/block/vpc.c > index 7fddbf0..1533b6a 100644 > --- a/block/vpc.c > +++ b/block/vpc.c > @@ -597,6 +597,51 @@ static coroutine_fn int vpc_co_write(BlockDriverState > *bs, int64_t sector_num, > return ret; > } > > +static int64_t coroutine_fn vpc_co_get_block_status(BlockDriverState *bs, > + int64_t sector_num, int nb_sectors, int *pnum) > +{ > + BDRVVPCState *s = bs->opaque; > + VHDFooter *footer = (VHDFooter*) s->footer_buf; > + int64_t start, offset, next; > + bool allocated; > + int n; > + > + if (be32_to_cpu(footer->type) == VHD_FIXED) { > + *pnum = nb_sectors; > + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA | > + (sector_num << BDRV_SECTOR_BITS); > + } > + > + offset = get_sector_offset(bs, sector_num, 0); > + start = offset; > + allocated = (offset != -1); > + *pnum = 0; > + > + do { > + /* All sectors in a block are contiguous (without using the > bitmap) */ > + n = ROUND_UP(sector_num + 1, s->block_size / BDRV_SECTOR_SIZE) > + - sector_num; > + n = MIN(n, nb_sectors); > + > + *pnum += n; > + sector_num += n; > + nb_sectors -= n; > + next = start + (*pnum * BDRV_SECTOR_SIZE); > + > + if (nb_sectors == 0) { > + break; > + } > + > + offset = get_sector_offset(bs, sector_num, 0); > + } while ((allocated && offset == next) || (!allocated && offset == -1)); > + > + if (allocated) { > + return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID | start; > + } else { > + return 0;
Shouldn't this be return BDRV_BLOCK_ZERO; ? vpc_read memsets all blocks with offset == -1 to 0x00. Not for this patch, but couldn't we use your new function to signifincantly speed up reading of continous allocated areas in vpc_read? Peter
