From: Nir Soffer <nsoffer@redhat.com>
To: Eric Blake <eblake@redhat.com>
Cc: qemu-block <qemu-block@nongnu.org>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
QEMU Developers <qemu-devel@nongnu.org>,
libguestfs@redhat.com
Subject: Re: [RFC libnbd PATCH] info: Add support for new qemu:joint-allocation
Date: Thu, 10 Jun 2021 01:20:13 +0300 [thread overview]
Message-ID: <CAMRbyysYRyALDan9D0L-FphGqQLUOkKrKp0eg0iP8ThHnSatgw@mail.gmail.com> (raw)
In-Reply-To: <20210609213154.1012848-1-eblake@redhat.com>
On Thu, Jun 10, 2021 at 12:32 AM Eric Blake <eblake@redhat.com> wrote:
>
> Qemu is adding qemu:joint-allocation as a single context combining the
> two bits of base:allocation and a compression of qemu:allocation-depth
> into two bits [1]. Decoding the bits makes it easier for humans to
> see the result of that context.
>
> [1] https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02446.html
> ---
>
> Obviously, this libnbd patch should only go in if the qemu RFC is
> accepted favorably. With this patch applied, the example listed in my
> qemu patch 2/2 commit message [2] becomes
>
> $ ~/libnbd/run nbdinfo --map=qemu:joint-allocation nbd://localhost
> 0 65536 3 hole,zero,unallocated
> 65536 65536 4 allocated,local
> 131072 65536 7 hole,zero,local
> 196608 65536 3 hole,zero,unallocated
>
> [2] https://lists.gnu.org/archive/html/qemu-devel/2021-06/msg02448.html
>
> For what it's worth, you can also play with the qemu+libnbd patches at:
> https://repo.or.cz/qemu/ericb.git/ master
> https://repo.or.cz/libnbd/ericb.git/ master
>
> (I sometimes rewind those branches, but they'll be stable for at least
> a few days after this email)
>
> info/map.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/info/map.c b/info/map.c
> index ae6d4fe..21e8657 100644
> --- a/info/map.c
> +++ b/info/map.c
> @@ -226,6 +226,27 @@ extent_description (const char *metacontext, uint32_t type)
> return ret;
> }
> }
> + else if (strcmp (metacontext, "qemu:joint-allocation") == 0) {
> + /* Combo of base:allocation and stripped-down qemu:allocation-depth */
> + const char *base, *depth;
> + switch (type & 3) {
> + case 0: base = "allocated"; break;
> + case 1: base = "hole"; break;
> + case 2: base = "zero"; break;
> + case 3: base = "hole,zero"; break;
> + }
> + switch (type & 0xc) {
> + case 0: depth = "unallocated"; break;
Is this possible? qemu reports BDRV_BLOCK_DATA but not BDRV_BLOCK_ALLOCATED?
Anyway this seems like a valid way to present qemu response.
> + case 4: depth = "local"; break;
> + case 8: depth = "backing"; break;
> + case 12: depth = "<unexpected depth>"; break;
This should not be possible based on the qemu patch, but printing this
seems like a good solution, and can help to debug such an issue.
Thinking about client code trying to copy extents based on the flags,
the client should abort the operation since qemu response is invalid.
> + }
> + if (asprintf (&ret, "%s,%s", base, depth) == -1) {
> + perror ("asprintf");
> + exit (EXIT_FAILURE);
> + }
> + return ret;
> + }
>
> return NULL; /* Don't know - description field will be omitted. */
> }
> --
> 2.31.1
>
next prev parent reply other threads:[~2021-06-09 22:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 18:01 [RFC PATCH 0/2] New NBD metacontext Eric Blake
2021-06-09 18:01 ` [PATCH 1/2] iotests: Improve and rename test 309 to nbd-qemu-allocation Eric Blake
2021-06-10 12:14 ` Vladimir Sementsov-Ogievskiy
2021-06-09 18:01 ` [PATCH 2/2] nbd: Add new qemu:joint-allocation metadata context Eric Blake
2021-06-09 23:52 ` Nir Soffer
2021-06-10 12:30 ` Vladimir Sementsov-Ogievskiy
2021-06-10 13:47 ` Eric Blake
2021-06-10 14:10 ` Vladimir Sementsov-Ogievskiy
2021-06-10 13:16 ` Nir Soffer
2021-06-10 14:04 ` Eric Blake
2021-06-10 14:43 ` Vladimir Sementsov-Ogievskiy
2021-06-10 13:31 ` Eric Blake
2021-06-11 23:39 ` Nir Soffer
2021-06-14 13:56 ` Eric Blake
2021-06-14 14:06 ` Nir Soffer
2021-06-09 21:31 ` [RFC libnbd PATCH] info: Add support for new qemu:joint-allocation Eric Blake
2021-06-09 22:20 ` Nir Soffer [this message]
2021-06-10 13:06 ` Eric Blake
2021-06-10 13:19 ` Nir Soffer
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