From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Max Reitz <mreitz@redhat.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>
Cc: Kevin Wolf <kwolf@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH v5 20/42] block/snapshot: Fall back to storage child
Date: Fri, 14 Jun 2019 16:47:54 +0000 [thread overview]
Message-ID: <c5a08e6f-d89c-28b2-803e-a9bf3f55b603@virtuozzo.com> (raw)
In-Reply-To: <bc1cdeca-2708-e122-c157-d08750e32ed6@redhat.com>
14.06.2019 19:10, Max Reitz wrote:
> On 14.06.19 17:22, Vladimir Sementsov-Ogievskiy wrote:
>> 13.06.2019 1:09, Max Reitz wrote:
>>> If the top node's driver does not provide snapshot functionality and we
>>> want to go down the chain, we should go towards the child which stores
>>> the data, i.e. the storage child.
>>>
>>> bdrv_snapshot_goto() becomes a bit weird because we may have to redirect
>>> the actual child pointer, so it only works if the storage child is
>>> bs->file or bs->backing (and then we have to find out which it is).
>>>
>>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>>> ---
>>> block/snapshot.c | 74 ++++++++++++++++++++++++++++++++++--------------
>>> 1 file changed, 53 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/block/snapshot.c b/block/snapshot.c
>>> index f2f48f926a..58cd667f3a 100644
>>> --- a/block/snapshot.c
>>> +++ b/block/snapshot.c
>>> @@ -154,8 +154,9 @@ int bdrv_can_snapshot(BlockDriverState *bs)
>>> }
>>>
>>> if (!drv->bdrv_snapshot_create) {
>>> - if (bs->file != NULL) {
>>> - return bdrv_can_snapshot(bs->file->bs);
>>> + BlockDriverState *storage_bs = bdrv_storage_bs(bs);
>>> + if (storage_bs) {
>>> + return bdrv_can_snapshot(storage_bs);
>>> }
>>> return 0;
>>> }
>>
>> Hmm is it correct at all doing a snapshot, when top format node doesn't support it,
>> metadata child doesn't support it and storage child supports? Doing snapshots of
>> storage child seems useless, as data file must be in sync with metadata.
>
> You’re right.
>
> That’s actually a bug already. VMDK can store data in multiple
> children, but it does not support snapshots. So if you store such a
> split VMDK disk on an RBD volume, it is possible that just the
> descriptor file is snapshotted, but nothing else.
>
> Hmmm. I think the best way is to check whether there is exactly one
> child that is not the bdrv_filtered_cow_child(). If so, we can go down
> to it and snapshot it. Otherwise, the node does not support snapshots.
>
Anything prevents format node to store something not in a bdrv child but in something separate?
May be the safest way is to fall back only for filter nodes.
--
Best regards,
Vladimir
next prev parent reply other threads:[~2019-06-14 16:53 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-12 22:09 [Qemu-devel] [PATCH v5 00/42] block: Deal with filters Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 01/42] block: Mark commit and mirror as filter drivers Max Reitz
2019-06-13 10:47 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 02/42] copy-on-read: Support compressed writes Max Reitz
2019-06-13 10:49 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 03/42] throttle: " Max Reitz
2019-06-13 10:51 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 04/42] block: Add child access functions Max Reitz
2019-06-13 12:15 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 05/42] block: Add chain helper functions Max Reitz
2019-06-13 12:26 ` Vladimir Sementsov-Ogievskiy
2019-06-13 12:33 ` Max Reitz
2019-06-13 12:39 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 06/42] qcow2: Implement .bdrv_storage_child() Max Reitz
2019-06-13 12:27 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 07/42] block: *filtered_cow_child() for *has_zero_init() Max Reitz
2019-06-13 12:34 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 08/42] block: bdrv_set_backing_hd() is about bs->backing Max Reitz
2019-06-13 12:40 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 09/42] block: Include filters when freezing backing chain Max Reitz
2019-06-13 13:04 ` Vladimir Sementsov-Ogievskiy
2019-06-13 14:05 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 10/42] block: Use CAF in bdrv_is_encrypted() Max Reitz
2019-06-13 13:16 ` Vladimir Sementsov-Ogievskiy
2019-06-13 14:15 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 11/42] block: Add bdrv_supports_compressed_writes() Max Reitz
2019-06-13 13:29 ` Vladimir Sementsov-Ogievskiy
2019-06-13 14:19 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 12/42] block: Use bdrv_filtered_rw* where obvious Max Reitz
2019-06-13 13:37 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 13/42] block: Use CAFs in block status functions Max Reitz
2019-06-14 12:07 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 14/42] block: Use CAFs when working with backing chains Max Reitz
2019-06-14 13:26 ` Vladimir Sementsov-Ogievskiy
2019-06-14 13:50 ` Max Reitz
2019-06-14 14:31 ` Vladimir Sementsov-Ogievskiy
2019-06-14 16:02 ` Max Reitz
2019-06-14 16:39 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 15/42] block: Re-evaluate backing file handling in reopen Max Reitz
2019-06-14 13:42 ` Vladimir Sementsov-Ogievskiy
2019-06-14 15:52 ` Max Reitz
2019-06-14 16:43 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 16/42] block: Use child access functions when flushing Max Reitz
2019-06-14 14:01 ` Vladimir Sementsov-Ogievskiy
2019-06-14 15:55 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 17/42] block: Use CAFs in bdrv_refresh_limits() Max Reitz
2019-06-14 15:04 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 18/42] block: Use CAFs in bdrv_refresh_filename() Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 19/42] block: Use CAF in bdrv_co_rw_vmstate() Max Reitz
2019-06-14 15:14 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 20/42] block/snapshot: Fall back to storage child Max Reitz
2019-06-14 15:22 ` Vladimir Sementsov-Ogievskiy
2019-06-14 16:10 ` Max Reitz
2019-06-14 16:47 ` Vladimir Sementsov-Ogievskiy [this message]
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 21/42] block: Use CAFs for debug breakpoints Max Reitz
2019-06-14 15:29 ` Vladimir Sementsov-Ogievskiy
2019-06-14 16:12 ` Max Reitz
2019-06-14 20:28 ` Eric Blake
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 22/42] block: Use CAFs in bdrv_get_allocated_file_size() Max Reitz
2019-06-12 22:17 ` Max Reitz
2019-06-14 15:41 ` Vladimir Sementsov-Ogievskiy
2019-06-14 16:15 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 23/42] blockdev: Use CAF in external_snapshot_prepare() Max Reitz
2019-06-14 15:46 ` Vladimir Sementsov-Ogievskiy
2019-06-14 16:20 ` Max Reitz
2019-06-14 16:58 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 24/42] block: Use child access functions for QAPI queries Max Reitz
2019-06-18 12:06 ` Vladimir Sementsov-Ogievskiy
2019-06-18 14:22 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 25/42] mirror: Deal with filters Max Reitz
2019-06-18 13:12 ` Vladimir Sementsov-Ogievskiy
2019-06-18 14:47 ` Max Reitz
2019-06-18 14:55 ` Vladimir Sementsov-Ogievskiy
2019-06-18 15:20 ` Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 26/42] backup: " Max Reitz
2019-06-18 13:45 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 27/42] commit: " Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 28/42] stream: " Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 29/42] nbd: Use CAF when looking for dirty bitmap Max Reitz
2019-06-18 13:58 ` Vladimir Sementsov-Ogievskiy
2019-06-18 14:48 ` Eric Blake
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 30/42] qemu-img: Use child access functions Max Reitz
2019-06-19 9:18 ` Vladimir Sementsov-Ogievskiy
2019-06-19 15:49 ` Max Reitz
2019-06-21 13:15 ` Vladimir Sementsov-Ogievskiy
2019-07-24 9:54 ` Vladimir Sementsov-Ogievskiy
2019-07-25 16:34 ` Max Reitz
2019-07-26 13:44 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 31/42] block: Drop backing_bs() Max Reitz
2019-06-19 9:18 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 32/42] block: Make bdrv_get_cumulative_perm() public Max Reitz
2019-06-19 9:19 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 33/42] blockdev: Fix active commit choice Max Reitz
2019-06-19 9:31 ` Vladimir Sementsov-Ogievskiy
2019-06-19 15:59 ` Max Reitz
2019-06-21 13:26 ` Vladimir Sementsov-Ogievskiy
2019-07-24 9:54 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 34/42] block: Inline bdrv_co_block_status_from_*() Max Reitz
2019-06-19 9:34 ` Vladimir Sementsov-Ogievskiy
2019-06-19 16:01 ` Max Reitz
2019-06-19 16:07 ` Max Reitz
2019-06-21 13:39 ` Vladimir Sementsov-Ogievskiy
2019-07-24 9:54 ` Vladimir Sementsov-Ogievskiy
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 35/42] block: Fix check_to_replace_node() Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 36/42] iotests: Add tests for mirror @replaces loops Max Reitz
2019-06-12 22:09 ` [Qemu-devel] [PATCH v5 37/42] block: Leave BDS.backing_file constant Max Reitz
2019-06-12 22:10 ` [Qemu-devel] [PATCH v5 38/42] iotests: Let complete_and_wait() work with commit Max Reitz
2019-06-12 22:10 ` [Qemu-devel] [PATCH v5 39/42] iotests: Add filter commit test cases Max Reitz
2019-06-12 22:10 ` [Qemu-devel] [PATCH v5 40/42] iotests: Add filter mirror " Max Reitz
2019-06-12 22:10 ` [Qemu-devel] [PATCH v5 41/42] iotests: Add test for commit in sub directory Max Reitz
2019-06-12 22:10 ` [Qemu-devel] [PATCH v5 42/42] iotests: Test committing to overridden backing Max Reitz
2019-06-13 15:28 ` [Qemu-devel] [PATCH v5 00/42] block: Deal with filters Vladimir Sementsov-Ogievskiy
2019-06-13 16:12 ` Max Reitz
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