linux-kernel - Re: [PATCH 4.14 01/51] scsi: libsas: direct call probe and destruct

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Date:   Mon, 3 Aug 2020 13:57:14 +0100
From:   John Garry <john.garry@...wei.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        yanaijie <yanaijie@...wei.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Ewan Milne <emilne@...hat.com>, Christoph Hellwig <hch@....de>,
        Tomas Henzl <thenzl@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Hannes Reinecke <hare@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.14 01/51] scsi: libsas: direct call probe and destruct

On 03/08/2020 13:19, Greg Kroah-Hartman wrote:
> From: Jason Yan <yanaijie@...wei.com>
> 
> [ Upstream commit 0558f33c06bb910e2879e355192227a8e8f0219d ]
> 

Hi Greg,

This patch was one of a series from Jason to fix this WARN issue, below:

https://lore.kernel.org/linux-scsi/8f6e3763-2b04-23e8-f1ec-8ed3c58f55d3@huawei.com/

I'm doubtful that it should be taken in isolation. Maybe 1 or 2 other 
patches are required.

The WARN was really annoying, so we could spend a bit of time to test a 
backport of what is strictly required. Let us know.

Thanks,
John

> In commit 87c8331fcf72 ("[SCSI] libsas: prevent domain rediscovery
> competing with ata error handling") introduced disco mutex to prevent
> rediscovery competing with ata error handling and put the whole
> revalidation in the mutex. But the rphy add/remove needs to wait for the
> error handling which also grabs the disco mutex. This may leads to dead
> lock.So the probe and destruct event were introduce to do the rphy
> add/remove asynchronously and out of the lock.
> 
> The asynchronously processed workers makes the whole discovery process
> not atomic, the other events may interrupt the process. For example,
> if a loss of signal event inserted before the probe event, the
> sas_deform_port() is called and the port will be deleted.
> 
> And sas_port_delete() may run before the destruct event, but the
> port-x:x is the top parent of end device or expander. This leads to
> a kernel WARNING such as:
> 
> [   82.042979] sysfs group 'power' not found for kobject 'phy-1:0:22'
> [   82.042983] ------------[ cut here ]------------
> [   82.042986] WARNING: CPU: 54 PID: 1714 at fs/sysfs/group.c:237
> sysfs_remove_group+0x94/0xa0
> [   82.043059] Call trace:
> [   82.043082] [<ffff0000082e7624>] sysfs_remove_group+0x94/0xa0
> [   82.043085] [<ffff00000864e320>] dpm_sysfs_remove+0x60/0x70
> [   82.043086] [<ffff00000863ee10>] device_del+0x138/0x308
> [   82.043089] [<ffff00000869a2d0>] sas_phy_delete+0x38/0x60
> [   82.043091] [<ffff00000869a86c>] do_sas_phy_delete+0x6c/0x80
> [   82.043093] [<ffff00000863dc20>] device_for_each_child+0x58/0xa0
> [   82.043095] [<ffff000008696f80>] sas_remove_children+0x40/0x50
> [   82.043100] [<ffff00000869d1bc>] sas_destruct_devices+0x64/0xa0
> [   82.043102] [<ffff0000080e93bc>] process_one_work+0x1fc/0x4b0
> [   82.043104] [<ffff0000080e96c0>] worker_thread+0x50/0x490
> [   82.043105] [<ffff0000080f0364>] kthread+0xfc/0x128
> [   82.043107] [<ffff0000080836c0>] ret_from_fork+0x10/0x50
> 
> Make probe and destruct a direct call in the disco and revalidate function,
> but put them outside the lock. The whole discovery or revalidate won't
> be interrupted by other events. And the DISCE_PROBE and DISCE_DESTRUCT
> event are deleted as a result of the direct call.
> 
> Introduce a new list to destruct the sas_port and put the port delete after
> the destruct. This makes sure the right order of destroying the sysfs
> kobject and fix the warning above.
> 
> In sas_ex_revalidate_domain() have a loop to find all broadcasted
> device, and sometimes we have a chance to find the same expander twice.
> Because the sas_port will be deleted at the end of the whole revalidate
> process, sas_port with the same name cannot be added before this.
> Otherwise the sysfs will complain of creating duplicate filename. Since
> the LLDD will send broadcast for every device change, we can only
> process one expander's revalidation.
> 
> [mkp: kbuild test robot warning]
> 
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> CC: John Garry <john.garry@...wei.com>
> CC: Johannes Thumshirn <jthumshirn@...e.de>
> CC: Ewan Milne <emilne@...hat.com>
> CC: Christoph Hellwig <hch@....de>
> CC: Tomas Henzl <thenzl@...hat.com>
> CC: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Hannes Reinecke <hare@...e.com>
> Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---