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 v5 33/42] blockdev: Fix active commit choice
Date: Wed, 19 Jun 2019 17:59:00 +0200 [thread overview]
Message-ID: <761c245d-3bb3-5fb3-21e4-0085caaffd2a@redhat.com> (raw)
In-Reply-To: <2670e61d-6c9b-9499-8e41-01c294379e47@virtuozzo.com>
[-- Attachment #1.1: Type: text/plain, Size: 3530 bytes --]
On 19.06.19 11:31, Vladimir Sementsov-Ogievskiy wrote:
> 13.06.2019 1:09, Max Reitz wrote:
>> We have to perform an active commit whenever the top node has a parent
>> that has taken the WRITE permission on it.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>> blockdev.c | 24 +++++++++++++++++++++---
>> 1 file changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/blockdev.c b/blockdev.c
>> index a464cabf9e..5370f3b738 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -3294,6 +3294,7 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
>> */
>> BlockdevOnError on_error = BLOCKDEV_ON_ERROR_REPORT;
>> int job_flags = JOB_DEFAULT;
>> + uint64_t top_perm, top_shared;
>>
>> if (!has_speed) {
>> speed = 0;
>> @@ -3406,14 +3407,31 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
>> goto out;
>> }
>>
>> - if (top_bs == bs) {
>> + /*
>> + * Active commit is required if and only if someone has taken a
>> + * WRITE permission on the top node. Historically, we have always
>> + * used active commit for top nodes, so continue that practice.
>> + * (Active commit is never really wrong.)
>
> Hmm, if we start active commit when nobody has write access, than
> we leave a possibility to someone to get this access during commit.
Isn’t that blocked by the commit filter? If it isn’t, it should be.
> And during
> passive commit write access is blocked. So, may be right way is do active commit
> always? Benefits:
> 1. One code path. and it shouldn't be worse when no writers, without guest writes
> mirror code shouldn't work worse than passive commit, if it is, it should be fixed.
> 2. Possibility of write access if user needs it during commit
> 3. I'm sure that active commit (mirror code) actually works faster, as it uses
> async requests and smarter handling of block status.
Disadvantage: Something may break because the basic commit job does not
emit BLOCK_JOB_READY and thus does not require block-job-complete.
Technically everything should expect jobs to potentially emit
BLOCK_JOB_READY, but who knows. I think we’d want at least a
deprecation period.
Max
>> + */
>> + bdrv_get_cumulative_perm(top_bs, &top_perm, &top_shared);
>> + if (top_perm & BLK_PERM_WRITE ||
>> + bdrv_skip_rw_filters(top_bs) == bdrv_skip_rw_filters(bs))
>> + {
>> if (has_backing_file) {
>> error_setg(errp, "'backing-file' specified,"
>> " but 'top' is the active layer");
>> goto out;
>> }
>> - commit_active_start(has_job_id ? job_id : NULL, bs, base_bs,
>> - job_flags, speed, on_error,
>> + if (!has_job_id) {
>> + /*
>> + * Emulate here what block_job_create() does, because it
>> + * is possible that @bs != @top_bs (the block job should
>> + * be named after @bs, even if @top_bs is the actual
>> + * source)
>> + */
>> + job_id = bdrv_get_device_name(bs);
>> + }
>> + commit_active_start(job_id, top_bs, base_bs, job_flags, speed, on_error,
>> filter_node_name, NULL, NULL, false, &local_err);
>> } else {
>> BlockDriverState *overlay_bs = bdrv_find_overlay(bs, top_bs);
>>
>
>
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next prev parent reply other threads:[~2019-06-19 16:03 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
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 [this message]
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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