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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 25/42] mirror: Deal with filters
Date: Mon, 9 Sep 2019 09:41:07 +0200
Message-ID: <eeb204f4-6143-3f13-9a46-72ce3c86f65a@redhat.com> (raw)
In-Reply-To: <f3a78c1a-b396-d82e-7fcf-04669a9eb2c7@virtuozzo.com>

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On 03.09.19 10:32, Vladimir Sementsov-Ogievskiy wrote:
> 02.09.2019 17:35, Max Reitz wrote:
>> On 31.08.19 11:57, Vladimir Sementsov-Ogievskiy wrote:
>>> 09.08.2019 19:13, Max Reitz wrote:
>>>> This includes some permission limiting (for example, we only need to
>>>> take the RESIZE permission for active commits where the base is smaller
>>>> than the top).
>>>>
>>>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>>>> ---
>>>>    block/mirror.c | 117 ++++++++++++++++++++++++++++++++++++++-----------
>>>>    blockdev.c     |  47 +++++++++++++++++---
>>>>    2 files changed, 131 insertions(+), 33 deletions(-)
>>>>
>>>> diff --git a/block/mirror.c b/block/mirror.c
>>>> index 54bafdf176..6ddbfb9708 100644
>>>> --- a/block/mirror.c
>>>> +++ b/block/mirror.c
>>>> @@ -42,6 +42,7 @@ typedef struct MirrorBlockJob {
>>>>        BlockBackend *target;
>>>>        BlockDriverState *mirror_top_bs;
>>>>        BlockDriverState *base;
>>>> +    BlockDriverState *base_overlay;
>>>>    
>>>>        /* The name of the graph node to replace */
>>>>        char *replaces;
>>>> @@ -665,8 +666,10 @@ static int mirror_exit_common(Job *job)
>>>>                                 &error_abort);
>>>>        if (!abort && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
>>>>            BlockDriverState *backing = s->is_none_mode ? src : s->base;
>>>> -        if (backing_bs(target_bs) != backing) {
>>>> -            bdrv_set_backing_hd(target_bs, backing, &local_err);
>>>> +        BlockDriverState *unfiltered_target = bdrv_skip_rw_filters(target_bs);
>>>> +
>>>> +        if (bdrv_filtered_cow_bs(unfiltered_target) != backing) {
>>>> +            bdrv_set_backing_hd(unfiltered_target, backing, &local_err);
>>>>                if (local_err) {
>>>>                    error_report_err(local_err);
>>>>                    ret = -EPERM;
>>>> @@ -715,7 +718,7 @@ static int mirror_exit_common(Job *job)
>>>>         * valid.
>>>>         */
>>>>        block_job_remove_all_bdrv(bjob);
>>>> -    bdrv_replace_node(mirror_top_bs, backing_bs(mirror_top_bs), &error_abort);
>>>> +    bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
>>>>    
>>>>        /* We just changed the BDS the job BB refers to (with either or both of the
>>>>         * bdrv_replace_node() calls), so switch the BB back so the cleanup does
>>>> @@ -812,7 +815,8 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
>>>>                return 0;
>>>>            }
>>>>    
>>>> -        ret = bdrv_is_allocated_above(bs, base, false, offset, bytes, &count);
>>>> +        ret = bdrv_is_allocated_above(bs, s->base_overlay, true, offset, bytes,
>>>> +                                      &count);
>>>>            if (ret < 0) {
>>>>                return ret;
>>>>            }
>>>> @@ -908,7 +912,7 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
>>>>        } else {
>>>>            s->target_cluster_size = BDRV_SECTOR_SIZE;
>>>>        }
>>>> -    if (backing_filename[0] && !target_bs->backing &&
>>>> +    if (backing_filename[0] && !bdrv_backing_chain_next(target_bs) &&
>>>>            s->granularity < s->target_cluster_size) {
>>>>            s->buf_size = MAX(s->buf_size, s->target_cluster_size);
>>>>            s->cow_bitmap = bitmap_new(length);
>>>> @@ -1088,8 +1092,9 @@ static void mirror_complete(Job *job, Error **errp)
>>>>        if (s->backing_mode == MIRROR_OPEN_BACKING_CHAIN) {
>>>>            int ret;
>>>>    
>>>> -        assert(!target->backing);
>>>> -        ret = bdrv_open_backing_file(target, NULL, "backing", errp);
>>>> +        assert(!bdrv_backing_chain_next(target));
>>>
>>> Preexisting, but seems we may crash here, I don't see where it is checked before, to
>>> return error if there is some backing. And even if we do so, we don't prevent appearing
>>> of target backing during mirror operation.
>>
>> The idea is that MIRROR_OPEN_BACKING_CHAIN is set only when using
>> drive-mirror with mode=existing.  In this case, we also set
>> BDRV_O_NO_BACKING for the target.
>>
>> You’re right that a user could add a backing chain to the target during
>> the operation.  They really have to make an effort to shoot themselves
>> in the foot for this because the target must have an auto-generated node
>> name.
>>
>> I suppose the best would be not to open the backing chain if the target
>> node already has a backing child?
> 
> Hmm, but we still should generate an error, as we can't do what was requested.

But the user didn’t request anything.  They just specified an existing
file as the target with mode=existing, then (for whatever reason) made a
real effort to add a backing node to it (i.e. they had to look up the
target’s auto-generated node name), and then the job finishes.

The user didn’t request us to open the backing chain of the target.
They just requested to mirror to an existing file.  If they manually
override that existing file’s backing chain, I think it makes sense to
keep it that way.

Max

>>>> +        ret = bdrv_open_backing_file(bdrv_skip_rw_filters(target), NULL,
>>>> +                                     "backing", errp);
>>>>            if (ret < 0) {
>>>>                return;
>>>>            }


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  reply index

Thread overview: 132+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-09 16:13 [Qemu-devel] [PATCH v6 00/42] block: " 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
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 [this message]
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
2019-08-09 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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