ACK: [PATCH][SRU Bionic] ata: do not schedule hot plug if it is a sas host

[Stefan Bader]

On 03.05.2018 22:06, dann frazier wrote:
> From: Jason Yan <yanaijie at huawei.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1768948
> 
> We've got a kernel panic when using sata disk with sas controller:
> 
> [115946.152283] Unable to handle kernel NULL pointer dereference at virtual address 000007d8
> [115946.223963] CPU: 0 PID: 22175 Comm: kworker/0:1 Tainted: G   W OEL  4.14.0 #1
> [115946.232925] Workqueue: events ata_scsi_hotplug
> [115946.237938] task: ffff8021ee50b180 task.stack: ffff00000d5d0000
> [115946.244717] PC is at sas_find_dev_by_rphy+0x44/0x114
> [115946.250224] LR is at sas_find_dev_by_rphy+0x3c/0x114
> ......
> [115946.355701] Process kworker/0:1 (pid: 22175, stack limit = 0xffff00000d5d0000)
> [115946.363369] Call trace:
> [115946.456356] [<ffff000008878a9c>] sas_find_dev_by_rphy+0x44/0x114
> [115946.462908] [<ffff000008878b8c>] sas_target_alloc+0x20/0x5c
> [115946.469408] [<ffff00000885a31c>] scsi_alloc_target+0x250/0x308
> [115946.475781] [<ffff00000885ba30>] __scsi_add_device+0xb0/0x154
> [115946.481991] [<ffff0000088b520c>] ata_scsi_scan_host+0x180/0x218
> [115946.488367] [<ffff0000088b53d8>] ata_scsi_hotplug+0xb0/0xcc
> [115946.494801] [<ffff0000080ebd70>] process_one_work+0x144/0x390
> [115946.501115] [<ffff0000080ec100>] worker_thread+0x144/0x418
> [115946.507093] [<ffff0000080f2c98>] kthread+0x10c/0x138
> [115946.512792] [<ffff0000080855dc>] ret_from_fork+0x10/0x18
> 
> We found that Ding Xiang has reported a similar bug before:
> https://patchwork.kernel.org/patch/9179817/
> 
> And this bug still exists in mainline. Since libsas handles hotplug and
> device adding/removing itself, do not need to schedule ata hot plug task
> here if it is a sas host.
> 
> Signed-off-by: Jason Yan <yanaijie at huawei.com>
> Cc: Ding Xiang <dingxiang at huawei.com>
> Cc: stable at vger.kernel.org
> Signed-off-by: Tejun Heo <tj at kernel.org>
> (cherry picked from commit 6f54120e17e311fd7ac42b9ec2a0611caa5b46ad)
> Signed-off-by: dann frazier <dann.frazier at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
>  drivers/ata/libata-eh.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
> index 11c3137d7b0a..c016829a38fd 100644
> --- a/drivers/ata/libata-eh.c
> +++ b/drivers/ata/libata-eh.c
> @@ -815,7 +815,8 @@ void ata_scsi_port_error_handler(struct Scsi_Host *host, struct ata_port *ap)
>  
>  	if (ap->pflags & ATA_PFLAG_LOADING)
>  		ap->pflags &= ~ATA_PFLAG_LOADING;
> -	else if (ap->pflags & ATA_PFLAG_SCSI_HOTPLUG)
> +	else if ((ap->pflags & ATA_PFLAG_SCSI_HOTPLUG) &&
> +		!(ap->flags & ATA_FLAG_SAS_HOST))
>  		schedule_delayed_work(&ap->hotplug_task, 0);
>  
>  	if (ap->pflags & ATA_PFLAG_RECOVERED)
> 


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