Re: [PATCH v5 6/7] scsi: libsas: direct call probe and destruct

[Hannes Reinecke]

On 12/08/2017 10:42 AM, Jason Yan wrote:
> 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.
> 
> Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
> CC: John Garry <john.garry@xxxxxxxxxx>
> CC: Johannes Thumshirn <jthumshirn@xxxxxxx>
> CC: Ewan Milne <emilne@xxxxxxxxxx>
> CC: Christoph Hellwig <hch@xxxxxx>
> CC: Tomas Henzl <thenzl@xxxxxxxxxx>
> CC: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
>  drivers/scsi/libsas/sas_ata.c      |  1 -
>  drivers/scsi/libsas/sas_discover.c | 32 ++++++++++++++++++--------------
>  drivers/scsi/libsas/sas_expander.c |  8 +++-----
>  drivers/scsi/libsas/sas_internal.h |  1 +
>  drivers/scsi/libsas/sas_port.c     |  3 +++
>  include/scsi/libsas.h              |  3 +--
>  include/scsi/scsi_transport_sas.h  |  1 +
>  7 files changed, 27 insertions(+), 22 deletions(-)
> 
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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