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

[Vladimir Sementsov-Ogievskiy]

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?

-- 
Best regards,
Vladimir