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Thu Mar 4 08:14:59 2021 X-Transaction-ID: 8cd137a54d4d4cbb897ce07afb08d71e X-filter-score: filter<0> X-Real-From: changlm@chinatelecom.cn X-Receive-IP: 172.18.0.92 X-MEDUSA-Status: 0 Date: Thu, 4 Mar 2021 08:14:50 +0800 From: ChangLimin To: "Nir Soffer" Subject: Re: [PATCH] file-posix: allow -EBUSY errors during write zeros on block References: <2021030209564214018344@chinatelecom.cn>, X-Priority: 3 X-GUID: F61C77F6-27CB-4C9D-83D0-A8A0BC26DD66 X-Has-Attach: no X-Mailer: Foxmail 7.2.17.58[cn] Mime-Version: 1.0 Message-ID: <2021030408145060119660@chinatelecom.cn> Content-Type: multipart/alternative; boundary="----=_001_NextPart850427742781_=----" Received-SPF: pass client-ip=42.123.76.219; envelope-from=changlm@chinatelecom.cn; helo=chinatelecom.cn X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, HTML_MESSAGE=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf , qemu-devel , qemu-block , mreitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is a multi-part message in MIME format. ------=_001_NextPart850427742781_=---- Content-Type: text/plain; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable = =0A
>> After Linux 5.10, write zeros to a multipath device using
>> ioctl(fd, BLKZEROOUT, range) with cache none or directsync = will return EBUSY.
>>
>> Similar to handle= _aiocb_write_zeroes_unmap, handle_aiocb_write_zeroes_block
>&= gt; allow -EBUSY errors during ioctl(fd, BLKZEROOUT, range).
>= ;>
>> Reference commit in Linux 5.10:
>>= ; https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/= ?id=3D384d87ef2c954fc58e6c5fd8253e4a1984f5fe02
> 
<= div>>But this can happen only when the block device is used by a file s= ystem or
>maybe someone else. In qemu we assume that we are t= he only user of the
>block device, so EBUSY is a fatal error = that should never happen, no?
> 
>Can you e= xplain a real world use case when we get EBUSY?
> 
=
>Nir
> 

Please refer to= https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/= html/configuring_device_mapper_multipath/index
Where multipath i= s configured to a SAN LUN, ioctl(fd, BLKZEROOUT, range)
to the /= dev/dm-x return EBUSY permanently since Linux 5.10.

ChangLimin

>> Signed-off-by: ChangLimin = <changlm@chinatelecom.cn>
>> ---
>> =  block/file-posix.c | 7 ++++++-
>>  1 file chang= ed, 6 insertions(+), 1 deletion(-)
>>
>> d= iff --git a/block/file-posix.c b/block/file-posix.c
>> ind= ex 05079b40ca..3e60c96214 100644
>> --- a/block/file-posix= .c
>> +++ b/block/file-posix.c
>> @@ -1629= ,8 +1629,13 @@ static ssize_t handle_aiocb_write_zeroes_block(RawPosixAIOD= ata *aiocb)
>>          } while (= errno =3D=3D EINTR);
>>
>>     &= nbsp;    ret =3D translate_err(-errno);
>> - &nb= sp;      if (ret =3D=3D -ENOTSUP) {
>> + &n= bsp;      switch (ret) {
>> +    =    case -ENOTSUP:
>> +       &nb= sp;case -EINVAL:
>> +        case -EBU= SY:
>>              s-&= gt;has_write_zeroes =3D false;
>> +       &= nbsp;    return -ENOTSUP;
>> +     &nb= sp;      break;
>>       &nb= sp;  }
>>      }
>> &n= bsp;#endif
>> --
>> 2.27.0
>&= gt;
=0A
 
=0A
 
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