From: Max Reitz <mreitz@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.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 v6 22/42] block: Fix bdrv_get_allocated_file_size's fallback
Date: Mon, 12 Aug 2019 21:15:38 +0200 [thread overview]
Message-ID: <42ba1ef7-0073-42f6-76f1-b3537f56f96b@redhat.com> (raw)
In-Reply-To: <994ec2e4-23fe-58d2-bc4e-120ec1e89d25@virtuozzo.com>
[-- Attachment #1.1: Type: text/plain, Size: 3597 bytes --]
On 12.08.19 19:14, Vladimir Sementsov-Ogievskiy wrote:
> 12.08.2019 16:09, Max Reitz wrote:
>> On 10.08.19 18:41, Vladimir Sementsov-Ogievskiy wrote:
>>> 09.08.2019 19:13, Max Reitz wrote:
>>>> If the driver does not implement bdrv_get_allocated_file_size(), we
>>>> should fall back to cumulating the allocated size of all non-COW
>>>> children instead of just bs->file.
>>>>
>>>> Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>>>> ---
>>>> block.c | 22 ++++++++++++++++++++--
>>>> 1 file changed, 20 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/block.c b/block.c
>>>> index 1070aa1ba9..6e1ddab056 100644
>>>> --- a/block.c
>>>> +++ b/block.c
>>>> @@ -4650,9 +4650,27 @@ int64_t bdrv_get_allocated_file_size(BlockDriverState *bs)
>>>> if (drv->bdrv_get_allocated_file_size) {
>>>> return drv->bdrv_get_allocated_file_size(bs);
>>>> }
>>>> - if (bs->file) {
>>>> - return bdrv_get_allocated_file_size(bs->file->bs);
>>>> +
>>>> + if (!QLIST_EMPTY(&bs->children)) {
>>>> + BdrvChild *child;
>>>> + int64_t child_size, total_size = 0;
>>>> +
>>>> + QLIST_FOREACH(child, &bs->children, next) {
>>>> + if (child == bdrv_filtered_cow_child(bs)) {
>>>> + /* Ignore COW backing files */
>>>> + continue;
>>>> + }
>>>> +
>>>> + child_size = bdrv_get_allocated_file_size(child->bs);
>>>> + if (child_size < 0) {
>>>> + return child_size;
>>>> + }
>>>> + total_size += child_size;
>>>> + }
>>>> +
>>>> + return total_size;
>>>> }
>>>> +
>>>> return -ENOTSUP;
>>>> }
>>>>
>>>>
>>>
>>> Hmm..
>>>
>>> 1. No children -> -ENOTSUP
>>> 2. Only cow child -> 0
>>> 3. Some non-cow children -> SUM
>>>
>>> It's all arguable (the strictest way is -ENOTSUP in either case),
>>> but if we want to fallback to SUM of non-cow children, 1. and 2. should return
>>> the same.
>>
>> I don’t think 2 is possible at all. If you have a COW child, you need
>> some other child to COW to.
>>
>> And in the weird (and probably impossible) case where a node really only
>> has a COW child, I’d say it’s correct that it has a disk size of 0 –
>> because it hasn’t COWed anything yet. (Just like a new qcow2 image with
>> a backing file only has its metadata as its disk size.)
>>
>
> Agreed. Then, why not return 0 on [1] ?
(1) Because that’s the current behavior. :-)
(2) Nodes that have no children are protocol nodes. Protocol nodes
(apart from null) still have to store their data somewhere. Therefore,
they must implement .bdrv_get_allocated_file_size() to report that. If
they don’t, that doesn’t mean they don’t store any data, but only that
we don’t know how much data they store.
> Also, another idea: shouldn't we return 0 for filters, i.e. skip filtered_rw_child too?
> [as filtered-child is more like backing child than file one, it's "less owned" by its parent]
Why would we do that? If I have a block device with a throttle node
attached to it and request how much space it uses, of course I will want
to know how much space the whole tree below it uses.
(Otherwise, bdrv_get_allocated_file_size() should only report anything
for protocol nodes, and 0 for everything else.)
Max
> with or without any of these suggestions:
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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next prev parent reply other threads:[~2019-08-12 19:16 UTC|newest]
Thread overview: 136+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 16:13 [Qemu-devel] [PATCH v6 00/42] block: Deal with filters Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 01/42] block: Mark commit and mirror as filter drivers Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 02/42] copy-on-read: Support compressed writes Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 03/42] throttle: " Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 04/42] block: Add child access functions Max Reitz
2019-08-09 16:56 ` Eric Blake
2019-09-04 16:16 ` Kevin Wolf
2019-09-09 7:56 ` Max Reitz
2019-09-09 9:36 ` Kevin Wolf
2019-09-09 14:04 ` Max Reitz
2019-09-09 16:13 ` Kevin Wolf
2019-09-10 9:14 ` Max Reitz
2019-09-10 10:47 ` Kevin Wolf
2019-09-10 11:36 ` Max Reitz
2019-09-10 12:48 ` Kevin Wolf
2019-09-10 12:59 ` Max Reitz
2019-09-10 13:10 ` Kevin Wolf
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 05/42] block: Add chain helper functions Max Reitz
2019-08-09 17:01 ` Eric Blake
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 06/42] qcow2: Implement .bdrv_storage_child() Max Reitz
2019-08-09 17:07 ` Eric Blake
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 07/42] block: *filtered_cow_child() for *has_zero_init() Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 08/42] block: bdrv_set_backing_hd() is about bs->backing Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 09/42] block: Include filters when freezing backing chain Max Reitz
2019-08-10 13:32 ` Vladimir Sementsov-Ogievskiy
2019-08-12 12:56 ` Max Reitz
2019-09-05 13:05 ` Kevin Wolf
2019-09-09 8:02 ` Max Reitz
2019-09-09 9:40 ` Kevin Wolf
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 10/42] block: Drop bdrv_is_encrypted() Max Reitz
2019-08-10 13:42 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 11/42] block: Add bdrv_supports_compressed_writes() Max Reitz
2019-09-05 13:11 ` Kevin Wolf
2019-09-09 8:09 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 12/42] block: Use bdrv_filtered_rw* where obvious Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 13/42] block: Use CAFs in block status functions Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 14/42] block: Use CAFs when working with backing chains Max Reitz
2019-08-10 15:19 ` Vladimir Sementsov-Ogievskiy
2019-09-05 14:05 ` Kevin Wolf
2019-09-09 8:25 ` Max Reitz
2019-09-09 9:55 ` Kevin Wolf
2019-09-09 14:08 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 15/42] block: Re-evaluate backing file handling in reopen Max Reitz
2019-08-10 16:05 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 16/42] block: Flush all children in generic code Max Reitz
2019-08-10 15:36 ` Vladimir Sementsov-Ogievskiy
2019-08-12 12:58 ` Max Reitz
2019-09-05 16:24 ` Kevin Wolf
2019-09-09 8:31 ` Max Reitz
2019-09-09 10:01 ` Kevin Wolf
2019-09-09 14:15 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 17/42] block: Use CAFs in bdrv_refresh_limits() Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 18/42] block: Use CAFs in bdrv_refresh_filename() Max Reitz
2019-08-10 16:22 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 19/42] block: Use CAF in bdrv_co_rw_vmstate() Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 20/42] block/snapshot: Fix fallback Max Reitz
2019-08-10 16:34 ` Vladimir Sementsov-Ogievskiy
2019-08-12 13:06 ` Max Reitz
2019-09-10 11:56 ` Kevin Wolf
2019-09-10 12:04 ` Max Reitz
2019-09-10 12:49 ` Kevin Wolf
2019-09-10 13:06 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 21/42] block: Use CAFs for debug breakpoints Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 22/42] block: Fix bdrv_get_allocated_file_size's fallback Max Reitz
2019-08-10 16:41 ` Vladimir Sementsov-Ogievskiy
2019-08-12 13:09 ` Max Reitz
2019-08-12 17:14 ` Vladimir Sementsov-Ogievskiy
2019-08-12 19:15 ` Max Reitz [this message]
2019-09-10 14:52 ` Kevin Wolf
2019-09-11 6:20 ` Max Reitz
2019-09-11 6:55 ` Kevin Wolf
2019-09-11 7:37 ` Max Reitz
2019-09-11 8:27 ` Kevin Wolf
2019-09-11 10:00 ` Max Reitz
2019-09-11 10:31 ` Kevin Wolf
2019-09-11 11:00 ` Max Reitz
2019-09-12 10:34 ` Kevin Wolf
2019-11-14 13:11 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 23/42] blockdev: Use CAF in external_snapshot_prepare() Max Reitz
2019-09-10 15:02 ` Kevin Wolf
2019-09-11 6:21 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 24/42] block: Use child access functions for QAPI queries Max Reitz
2019-08-10 16:57 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 25/42] mirror: Deal with filters Max Reitz
2019-08-12 11:09 ` Vladimir Sementsov-Ogievskiy
2019-08-12 13:26 ` Max Reitz
2019-08-14 15:17 ` Vladimir Sementsov-Ogievskiy
2019-08-31 9:57 ` Vladimir Sementsov-Ogievskiy
2019-09-02 14:35 ` Max Reitz
2019-09-03 8:32 ` Vladimir Sementsov-Ogievskiy
2019-09-09 7:41 ` Max Reitz
2019-09-13 12:55 ` Kevin Wolf
2019-09-16 10:26 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 26/42] backup: " Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 27/42] commit: " Max Reitz
2019-08-31 10:44 ` Vladimir Sementsov-Ogievskiy
2019-09-02 14:55 ` Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 28/42] stream: " Max Reitz
2019-08-12 11:55 ` Vladimir Sementsov-Ogievskiy
2019-09-13 14:16 ` Kevin Wolf
2019-09-16 9:52 ` Max Reitz
2019-09-16 14:47 ` Kevin Wolf
2019-12-11 12:52 ` Max Reitz
2019-12-11 15:52 ` Kevin Wolf
2019-12-11 16:12 ` Max Reitz
2019-12-11 16:35 ` Kevin Wolf
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 29/42] nbd: Use CAF when looking for dirty bitmap Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 30/42] qemu-img: Use child access functions Max Reitz
2019-08-12 12:14 ` Vladimir Sementsov-Ogievskiy
2019-08-12 13:28 ` Max Reitz
2019-08-14 16:04 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 31/42] block: Drop backing_bs() Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 32/42] block: Make bdrv_get_cumulative_perm() public Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 33/42] blockdev: Fix active commit choice Max Reitz
2019-08-09 16:13 ` [Qemu-devel] [PATCH v6 34/42] block: Inline bdrv_co_block_status_from_*() Max Reitz
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 35/42] block: Fix check_to_replace_node() Max Reitz
2019-08-15 15:21 ` Vladimir Sementsov-Ogievskiy
2019-08-15 17:01 ` Max Reitz
2019-08-16 11:01 ` Vladimir Sementsov-Ogievskiy
2019-08-16 13:30 ` Max Reitz
2019-08-16 14:24 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 36/42] iotests: Add tests for mirror @replaces loops Max Reitz
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 37/42] block: Leave BDS.backing_file constant Max Reitz
2019-08-16 16:16 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 38/42] iotests: Let complete_and_wait() work with commit Max Reitz
2019-08-23 5:59 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 39/42] iotests: Add filter commit test cases Max Reitz
2019-08-31 11:41 ` Vladimir Sementsov-Ogievskiy
2019-09-02 15:06 ` Max Reitz
2019-08-31 12:35 ` Vladimir Sementsov-Ogievskiy
2019-09-02 15:09 ` Max Reitz
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 40/42] iotests: Add filter mirror " Max Reitz
2019-08-31 12:35 ` Vladimir Sementsov-Ogievskiy
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 41/42] iotests: Add test for commit in sub directory Max Reitz
2019-08-09 16:14 ` [Qemu-devel] [PATCH v6 42/42] iotests: Test committing to overridden backing Max Reitz
2019-09-03 9:18 ` Vladimir Sementsov-Ogievskiy
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