On Tue, Nov 12, 2013 at 11:28:05AM +0100, Kevin Wolf wrote:
> 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.
Then the name is inappropriate, how about bdrv_preallocate()?
>
> I wonder if this would be a correct implementation for a bdrv_anchor(),
Why?
> though. I also wouldn't call that full preallocation, but it might be
> useful anyway.
Wouldn't bdrv_preallocate(bs, 0, bdrv_getlength(bs)) be full
preallocation?
