From: Eric Blake <eblake@redhat.com>
To: Nir Soffer <nirsof@gmail.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Nir Soffer <nsoffer@redhat.com>,
Max Reitz <mreitz@redhat.com>
Subject: Re: [PATCH 1/2] block: nbd: Fix convert qcow2 compressed to nbd
Date: Mon, 27 Jul 2020 09:04:15 -0500 [thread overview]
Message-ID: <1737bdc4-6192-1adb-7027-faf09bdbd92c@redhat.com> (raw)
In-Reply-To: <20200726152532.256261-2-nsoffer@redhat.com>
On 7/26/20 10:25 AM, Nir Soffer wrote:
> When converting to qcow2 compressed format, the last step is a special
> zero length compressed write, ending in call to bdrv_co_truncate(). This
> call always fail for the nbd driver since it does not implement
fails
> bdrv_co_truncate().
Arguably, qemu-img should be taught to ignore the failure, since it is
not unique to the nbd driver. But I can live with your approach here.
>
> For block devices, which have the same limits, the call succeeds since
> file driver implements bdrv_co_truncate(). If the caller asked to
> truncate to the same or smaller size with exact=false, the truncate
> succeeds. Implement the same logic for nbd.
>
> Example failing without this change:
>
>
> Fixes: https://bugzilla.redhat.com/1860627
> Signed-off-by: Nir Soffer <nsoffer@redhat.com>
> ---
> block/nbd.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/block/nbd.c b/block/nbd.c
> index 65a4f56924..2154113af3 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -1966,6 +1966,30 @@ static void nbd_close(BlockDriverState *bs)
> nbd_clear_bdrvstate(s);
> }
>
> +/*
> + * NBD cannot truncate, but if the caller ask to truncate to the same size, or
asks
> + * to a smaller size with extact=false, there is not reason to fail the
exact, no
> + * operation.
> + */
> +static int coroutine_fn nbd_co_truncate(BlockDriverState *bs, int64_t offset,
> + bool exact, PreallocMode prealloc,
> + BdrvRequestFlags flags, Error **errp)
> +{
> + BDRVNBDState *s = bs->opaque;
> +
> + if (offset != s->info.size && exact) {
> + error_setg(errp, "Cannot resize NBD nodes");
> + return -ENOTSUP;
> + }
> +
> + if (offset > s->info.size) {
> + error_setg(errp, "Cannot grow NBD nodes");
> + return -EINVAL;
> + }
> +
> + return 0;
Looks reasonable. As Max said, I wonder if we want to reject particular
preallocation modes (looking at block/file-posix.c:raw_co_truncate), in
the case where the image was resized down and then back up (since
s->info.size is constant, but the BDS size is not if inexact resize
succeeds).
As you have a bugzilla entry, I think this is safe for -rc2; I'll be
touching up the typos and queuing it through my NBD tree later today.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2020-07-27 14:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-26 15:25 [PATCH 0/2] Fix convert to qcow2 compressed to NBD Nir Soffer
2020-07-26 15:25 ` [PATCH 1/2] block: nbd: Fix convert qcow2 compressed to nbd Nir Soffer
2020-07-27 8:58 ` Max Reitz
2020-07-27 14:04 ` Eric Blake [this message]
2020-07-27 14:52 ` Nir Soffer
2020-07-27 15:12 ` Nir Soffer
2020-07-26 15:25 ` [PATCH 2/2] qemu-iotests: Test convert to qcow2 compressed to NBD Nir Soffer
2020-07-27 10:04 ` Max Reitz
2020-07-27 14:14 ` Eric Blake
2020-07-27 14:35 ` Nir Soffer
2020-07-27 14:41 ` Eric Blake
2020-07-27 14:44 ` Nir Soffer
2020-07-27 14:44 ` Nir Soffer
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