Re: [libvirt] [Qemu-devel] [PATCH v3] qapi: add dirty-bitmaps to query-named-block-nodes result

On 7/24/19 12:47 AM, Markus Armbruster wrote: > John Snow <jsnow(a)redhat.com&gt; writes: > >> From: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; >> >> Let's add a possibility to query dirty-bitmaps not only on root nodes. >> It is useful when dealing both with snapshots and incremental backups. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; >> [Added deprecation information. --js] >> Signed-off-by: John Snow <jsnow(a)redhat.com&gt; >> --- >> block/qapi.c | 5 +++++ >> qapi/block-core.json | 6 +++++- >> qemu-deprecated.texi | 12 ++++++++++++ >> 3 files changed, 22 insertions(+), 1 deletion(-) >> >> diff --git a/block/qapi.c b/block/qapi.c >> index 917435f022..15f1030264 100644 >> --- a/block/qapi.c >> +++ b/block/qapi.c >> @@ -79,6 +79,11 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk, >> info->backing_file = g_strdup(bs->backing_file); >> } >> >> + if (!QLIST_EMPTY(&bs->dirty_bitmaps)) { >> + info->has_dirty_bitmaps = true; >> + info->dirty_bitmaps = bdrv_query_dirty_bitmaps(bs); >> + } >> + >> info->detect_zeroes = bs->detect_zeroes; >> >> if (blk && blk_get_public(blk)->throttle_group_member.throttle_state) { >> diff --git a/qapi/block-core.json b/qapi/block-core.json >> index 0d43d4f37c..9210ae233d 100644 >> --- a/qapi/block-core.json >> +++ b/qapi/block-core.json >> @@ -360,6 +360,9 @@ >> # @write_threshold: configured write threshold for the device. >> # 0 if disabled. (Since 2.3) >> # >> +# @dirty-bitmaps: dirty bitmaps information (only present if node >> +# has one or more dirty bitmaps) (Since 4.2) >> +# >> # Since: 0.14.0 >> # >> ## >> @@ -378,7 +381,7 @@ >> '*bps_wr_max_length': 'int', '*iops_max_length': 'int', >> '*iops_rd_max_length': 'int', '*iops_wr_max_length': 'int', >> '*iops_size': 'int', '*group': 'str', 'cache': 'BlockdevCacheInfo', >> - 'write_threshold': 'int' } } >> + 'write_threshold': 'int', '*dirty-bitmaps': ['BlockDirtyInfo'] } } >> >> ## >> # @BlockDeviceIoStatus: >> @@ -656,6 +659,7 @@ >> # >> # @dirty-bitmaps: dirty bitmaps information (only present if the >> # driver has one or more dirty bitmaps) (Since 2.0) >> +# Deprecated in 4.2; see BlockDirtyInfo instead. >> # >> # @io-status: @BlockDeviceIoStatus. Only present if the device >> # supports it and the VM is configured to stop on errors >> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi >> index c90b08d553..6374b66546 100644 >> --- a/qemu-deprecated.texi >> +++ b/qemu-deprecated.texi >> @@ -134,6 +134,18 @@ The ``status'' field of the ``BlockDirtyInfo'' structure, returned by >> the query-block command is deprecated. Two new boolean fields, >> ``recording'' and ``busy'' effectively replace it. >> >> +@subsection query-block result field dirty-bitmaps (Since 4.2) >> + >> +The ``dirty-bitmaps`` field of the ``BlockInfo`` structure, returned by >> +the query-block command is itself now deprecated. The ``dirty-bitmaps`` >> +field of the ``BlockDeviceInfo`` struct should be used instead, which is the >> +type of the ``inserted`` field in query-block replies, as well as the >> +type of array items in query-named-block-nodes. > > Would the text be clearer if it talked only about commands, not about > types? > > Here's my (laconic) try: > > @subsection query-block result field dirty-bitmaps (Since 4.2) > > In the result of query-block, member ``dirty-bitmaps'' has been moved > into member ``inserted''. > Yeah, that's probably better in terms of strictly what the deprecation is. I was trying to imply that the output will also now be visible in other commands as well, but that's not the deprecation -- that's the new feature. ACK > Aside: same for existing @subsection query-block result field > dirty-bitmaps[i].status (since 4.0). > (Probably not worth editing deprecation text that was already published.)

>> +Since the ``dirty-bitmaps`` field is optionally present in both the old and >> +new locations, clients must use introspection to learn where to anticipate >> +the field if/when it does appear in command output. >> + > > I find this hint a bit confusing. Do we need it? > I think so, yes: it's nice to inform readers of how to cope with the deprecation. > If yes, laconic me again: > > Clients should use introspection to learn whether ``dirty-bitmaps'' is > in the new location. > Too terse. I want my documentation to greet me in the morning by reading me the local newspaper while I brush my teeth. Yours says the "how", but I think a hint should have the "why": "Since the ``dirty-bitmaps`` field is not always present in command output, Clients should use introspection to learn the location of this field."

But I'm only willing to give you a self-deprecating joke and a final nudge to keep a more informative hint, and then I'll capitulate and take your suggestion if you give me a stern look.

--js >> @subsection query-cpus (since 2.12.0) >> >> The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command.