Am 12.11.2013 um 08:47 hat Hu Tao geschrieben:
> Implement bdrv_zero_init using posix_fallocate.
>
> Signed-off-by: Hu Tao <hu...@cn.fujitsu.com>
> ---
> block/raw-posix.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index f6d48bb..8798599 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1190,6 +1190,18 @@ static int64_t coroutine_fn
> raw_co_get_block_status(BlockDriverState *bs,
> return ret;
> }
>
> +static int raw_zero_init(BlockDriverState *bs, int64_t offset, int64_t
> length)
> +{
> + BDRVRawState *s = bs->opaque;
> + int64_t len = bdrv_getlength(bs);
> +
> + if (offset + length < 0 || offset + length > len) {
> + return -1;
> + }
> +
> + return posix_fallocate(s->fd, offset, length);
> +}
This doesn't really initialise anything to zero. It merely preallocates
those parts of a file that aren't allocated yet (and they happen to be
zeroed in this case), but leaves already existing parts untouched.
I wonder if this would be a correct implementation for a bdrv_anchor(),
though. I also wouldn't call that full preallocation, but it might be
useful anyway.
Kevin
