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Re: [Qemu-devel] [Fwd: [PATCH v2] vpc: Implement bdrv_co_get_block_statu
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [Fwd: [PATCH v2] vpc: Implement bdrv_co_get_block_status()] |
Date: |
Wed, 18 Feb 2015 22:03:23 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
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 <address@hidden>
> ---
> 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
- Re: [Qemu-devel] [Fwd: [PATCH v2] vpc: Implement bdrv_co_get_block_status()],
Peter Lieven <=