Re: [Qemu-devel] [PATCH v2 00/12] block: qiov_offset parameter for io

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

23.08.2019 19:21, Stefan Hajnoczi wrote:
> On Thu, Aug 22, 2019 at 05:59:43PM +0000, Vladimir Sementsov-Ogievskiy wrote:
>> 22.08.2019 20:39, Vladimir Sementsov-Ogievskiy wrote:
>>> 22.08.2019 20:24, Vladimir Sementsov-Ogievskiy wrote:
>>>> 22.08.2019 18:50, Stefan Hajnoczi wrote:
>>>>> On Tue, Jun 04, 2019 at 07:15:02PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>>>> Hi all!
>>>>>>
>>>>>> Here is new parameter qiov_offset for io path, to avoid
>>>>>> a lot of places with same pattern of creating local_qiov or hd_qiov
>>>>>> variables.
>>>>>>
>>>>>> These series also includes my
>>>>>> "[Qemu-devel] [PATCH 0/2] block/io: refactor padding"
>>>>>> with some changes [described in 01 and 03 emails]
>>>>>>
>>>>>> Vladimir Sementsov-Ogievskiy (12):
>>>>>>     util/iov: introduce qemu_iovec_init_extended
>>>>>>     util/iov: improve qemu_iovec_is_zero
>>>>>>     block/io: refactor padding
>>>>>>     block: define .*_part io handlers in BlockDriver
>>>>>>     block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
>>>>>>     block/io: bdrv_co_do_copy_on_readv: lazy allocation
>>>>>>     block/io: bdrv_aligned_preadv: use and support qiov_offset
>>>>>>     block/io: bdrv_aligned_pwritev: use and support qiov_offset
>>>>>>     block/io: introduce bdrv_co_p{read,write}v_part
>>>>>>     block/qcow2: refactor qcow2_co_preadv to use buffer-based io
>>>>>>     block/qcow2: implement .bdrv_co_preadv_part
>>>>>>     block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
>>>>>>
>>>>>>    block/qcow2.h             |   1 +
>>>>>>    include/block/block_int.h |  21 ++
>>>>>>    include/qemu/iov.h        |  10 +-
>>>>>>    block/backup.c            |   2 +-
>>>>>>    block/io.c                | 532 ++++++++++++++++++++++----------------
>>>>>>    block/qcow2-cluster.c     |  14 +-
>>>>>>    block/qcow2.c             | 131 +++++-----
>>>>>>    qemu-img.c                |   4 +-
>>>>>>    util/iov.c                | 153 +++++++++--
>>>>>>    9 files changed, 559 insertions(+), 309 deletions(-)
>>>>>
>>>>> qemu-iotests 077 fails after I apply this series (including your
>>>>> uninitialized variable fix).  I'm afraid I can't include it in the block
>>>>> pull request, sorry!
>>>>>
>>>>> Stefan
>>>>>
>>>>
>>>> Hmm, 77 don't work on master for me:
>>>> 077      fail       [20:23:57] [20:23:59]                    output mismatch (see 077.out.bad)
>>>> --- /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out     2019-04-22 15:06:56.162045432 +0300
>>>> +++ /work/src/qemu/up-block-drop-hd-qiov/tests/qemu-iotests/077.out.bad 2019-08-22 20:23:59.124122307 +0300
>>>> @@ -1,7 +1,15 @@
>>>>    QA output created by 077
>>>> +==117186==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117186==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffefc071000; bottom 0x7fad7277b000; size: 0x0051898f6000 (350200225792)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
>>>>
>>>>    == Some concurrent requests involving RMW ==
>>>> +==117197==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117197==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa4fcc000; bottom 0x7fa93a2c1000; size: 0x00566ad0b000 (371159248896)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    wrote XXX/XXX bytes at offset XXX
>>>>    XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    wrote XXX/XXX bytes at offset XXX
>>>> @@ -66,6 +74,10 @@
>>>>    XXX bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>
>>>>    == Verify image content ==
>>>> +==117219==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117219==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7ffc722de000; bottom 0x7f0848232000; size: 0x00f42a0ac000 (1048677367808)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    read 512/512 bytes at offset 0
>>>>    512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    read 512/512 bytes at offset 512
>>>> @@ -156,5 +168,9 @@
>>>>    1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>>    read 2048/2048 bytes at offset 71680
>>>>    2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>> +==117229==WARNING: ASan doesn't fully support makecontext/swapcontext functions and may produce false positives in some cases!
>>>> +==117229==WARNING: ASan is ignoring requested __asan_handle_no_return: stack top: 0x7fffa3342000; bottom 0x7fd85a275000; size: 0x0027490cd000 (168729300992)
>>>> +False positive error reports may follow
>>>> +For details see http://code.google.com/p/address-sanitizer/issues/detail?id=189
>>>>    No errors were found on the image.
>>>>    *** done
>>>> Failures: 077
>>>> Failed 1 of 1 tests
>>>>
>>>>
>>>>
>>>
>>> But after "block/io: refactor padding" it hangs instead of this fail.. This is not good
>>>
>>>
>>
>> Aha seems it's because 77 has "break pwritev_rmw_after_tail" which may not fire if we have merge_reads = true.
>>
>> So, for me the following fix for 03 helps (77 fails, but not hangs, so same behavior as on master):
>>
>> diff --git a/block/io.c b/block/io.c
>> index 6448f1c503..04e69400d8 100644
>> --- a/block/io.c
>> +++ b/block/io.c
>> @@ -1493,13 +1493,23 @@ static int bdrv_padding_rmw_read(BdrvChild *child,
>>
>>            qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
>>
>> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
>> +        if (pad->head) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
>> +        }
>> +        if (pad->merge_reads && pad->tail) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
>> +        }
>>            ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
>>                                      align, &local_qiov, 0);
>>            if (ret < 0) {
>>                return ret;
>>            }
>> -        bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
>> +        if (pad->head) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
>> +        }
>> +        if (pad->merge_reads && pad->tail) {
>> +            bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
>> +        }
>>
>>
>> Does it work for you?
> 
> Yes, it works as expected now, thanks.  I've squashed in your fix and
> will send these patches in the next block pull request.
> 

Thank you!


-- 
Best regards,
Vladimir