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From: Gulam Mohamed <gulam.mohamed@oracle.com>
To: kernel test robot <oliver.sang@intel.com>
CC: "oe-lkp@lists.linux.dev" <oe-lkp@lists.linux.dev>,
        "lkp@intel.com"
	<lkp@intel.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "ltp@lists.linux.it" <ltp@lists.linux.it>,
        "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>,
        "yukuai1@huaweicloud.com"
	<yukuai1@huaweicloud.com>,
        "hch@lst.de" <hch@lst.de>, "axboe@kernel.dk"
	<axboe@kernel.dk>
Subject: RE: [PATCH V4 for-6.10/block] loop: Fix a race between loop detach
 and loop open
Thread-Topic: [PATCH V4 for-6.10/block] loop: Fix a race between loop detach
 and loop open
Thread-Index: AQHavA/KpPG1Y2G/i0Skj77IBfr3QrHGM6eQ
Date: Thu, 13 Jun 2024 21:10:37 +0000
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 <IA1PR10MB7240B2686664744DB0D8867F98C12@IA1PR10MB7240.namprd10.prod.outlook.com>
References: <20240607190607.17705-1-gulam.mohamed@oracle.com>
 <202406112130.a572f72-oliver.sang@intel.com>
In-Reply-To: <202406112130.a572f72-oliver.sang@intel.com>
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Hi,

> -----Original Message-----
> From: kernel test robot <oliver.sang@intel.com>
> Sent: Tuesday, June 11, 2024 8:28 PM
> To: Gulam Mohamed <gulam.mohamed@oracle.com>
> Cc: oe-lkp@lists.linux.dev; lkp@intel.com; linux-block@vger.kernel.org;
> ltp@lists.linux.it; linux-kernel@vger.kernel.org; yukuai1@huaweicloud.com=
;
> hch@lst.de; axboe@kernel.dk; oliver.sang@intel.com
> Subject: Re: [PATCH V4 for-6.10/block] loop: Fix a race between loop deta=
ch
> and loop open
>=20
>=20
>=20
> Hello,
>=20
> kernel test robot noticed "ltp.ioctl09.fail" on:
>=20
> commit: 02ab74c165fb204557fe6cde80eda0633fbc4412 ("[PATCH V4 for-
> 6.10/block] loop: Fix a race between loop detach and loop open")
> url: https://urldefense.com/v3/__https://github.com/intel-lab-
> lkp/linux/commits/Gulam-Mohamed/loop-Fix-a-race-between-loop-detach-
> and-loop-open/20240608-
> 031123__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqqBaG_-
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVVA
> _7Fk4$
> base:
> https://urldefense.com/v3/__https://git.kernel.org/cgit/linux/kernel/git/=
axboe
> /linux-block.git__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqqBaG_-
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVSM
> 8EomQ$  for-next patch link:
> https://urldefense.com/v3/__https://lore.kernel.org/all/20240607190607.17=
7
> 05-1-
> gulam.mohamed@oracle.com/__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqq
> BaG_-
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVEcY
> Yz3s$
> patch subject: [PATCH V4 for-6.10/block] loop: Fix a race between loop de=
tach
> and loop open
>=20
> in testcase: ltp
> version: ltp-x86_64-14c1f76-1_20240608
> with following parameters:
>=20
> 	disk: 1HDD
> 	fs: ext4
> 	test: syscalls-03/ioctl09
>=20
>=20
>=20
> compiler: gcc-13
> test machine: 4 threads 1 sockets Intel(R) Core(TM) i3-3220 CPU @ 3.30GHz
> (Ivy Bridge) with 8G memory
>=20
> (please refer to attached dmesg/kmsg for entire log/backtrace)
>=20
>=20
>=20
>=20
> If you fix the issue in a separate patch/commit (i.e. not just a new vers=
ion of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Closes:
> | https://urldefense.com/v3/__https://lore.kernel.org/oe-lkp/20240611213
> | 0.a572f72-
> oliver.sang@intel.com__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqqBaG_
> | -
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVDgL
> 6MVc$
>=20
>=20
> Running tests.......
> <<<test_start>>>
> tag=3Dioctl09 stime=3D1717978971
> cmdline=3D"ioctl09"
> contacts=3D""
> analysis=3Dexit
> <<<test_output>>>
> tst_test.c:1734: TINFO: LTP version: 20240524-32-ge2c52c5bb
> tst_test.c:1618: TINFO: Timeout per run is 0h 02m 30s
> tst_device.c:96: TINFO: Found free device 0 '/dev/loop0'
> ioctl09.c:48: TPASS: access /sys/block/loop0/loop0p1 succeeds
> ioctl09.c:56: TPASS: access /dev/loop0p1 succeeds
> ioctl09.c:51: TPASS: access /sys/block/loop0/loop0p2 fails
> ioctl09.c:59: TPASS: access /dev/loop0p2 fails
> ioctl09.c:48: TPASS: access /sys/block/loop0/loop0p1 succeeds
> ioctl09.c:56: TPASS: access /dev/loop0p1 succeeds
> ioctl09.c:48: TPASS: access /sys/block/loop0/loop0p2 succeeds
> ioctl09.c:56: TPASS: access /dev/loop0p2 succeeds
> tst_device.c:263: TWARN: ioctl(/dev/loop0, LOOP_CLR_FD, 0) no ENXIO for
> too long
>=20
> Summary:
> passed   8
> failed   0
> broken   0
> skipped  0
> warnings 1
> incrementing stop
> <<<execution_status>>>
> initiation_status=3D"ok"
> duration=3D3 termination_type=3Dexited termination_id=3D4 corefile=3Dno
> cutime=3D3 cstime=3D42
> <<<test_end>>>
> INFO: ltp-pan reported some tests FAIL
> LTP Version: 20240524-32-ge2c52c5bb
>=20
>=20
> ###############################################################
>=20
>             Done executing testcases.
>             LTP Version:  20240524-32-ge2c52c5bb
>=20
> ###############################################################
>=20
>=20
>=20
>=20
> The kernel config and materials to reproduce are available at:
> https://urldefense.com/v3/__https://download.01.org/0day-
> ci/archive/20240611/202406112130.a572f72-
> oliver.sang@intel.com__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqqBaG_-
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVsf4L
> rkk$
>=20
>=20
>=20
> --
> 0-DAY CI Kernel Test Service
> https://urldefense.com/v3/__https://github.com/intel/lkp-
> tests/wiki__;!!ACWV5N9M2RV99hQ!Niww5tWxpW_rqqBaG_-
> w8CbDvJjcC6AwSb4gYZL3tS7fUrBcYesefSCbVL8GrWLJ0R8W_jyMsgUDi0HVQRs
> yTxc$

I looked at the LTP test case failure and also the function tst_detach_devi=
ce_by_fd() which failed. Our kernel patch will defer all the attempts to de=
tach a loop device to the last close, to fix an issue.
The tst_detach_device_by_fd() in LTP test case will open the loop device an=
d repeatedly checks for error code ENXIO. As the new approach, as I mention=
ed above, will defer the detach to last close and the last close happens *o=
nly* when the LTP test function tst_detach_device_by_fd() returns, the test=
 will obviously fail. So, Can you please modify the LTP test case to accomm=
odate the new behaviour of kernel code for loop detach?
Please let us know your comments.

Regards,
Gulam Mohamed.