linux-kernel - Re: [PATCH V2 resend] libata:fix kernel panic when hotplug

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Date:	Wed, 22 Jun 2016 14:46:24 +0800
From:	dingxiang <dingxiang@...wei.com>
To:	Tejun Heo <tj@...nel.org>, Dan Williams <dan.j.williams@...el.com>
CC:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	<jejb@...ux.vnet.ibm.com>, Wei Fang <fangwei1@...wei.com>,
	<miaoxie@...wei.com>, <wangyijing@...wei.com>,
	<zhangaihua1@...wei.com>, <zhaohongjiang@...wei.com>,
	<houtao1@...wei.com>, linux-scsi <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 resend] libata:fix kernel panic when hotplug


Hi,All
> Hello,
>
> On Mon, Jun 20, 2016 at 06:46:55PM -0700, Dan Williams wrote:
>> On Mon, Jun 20, 2016 at 6:22 PM, Martin K. Petersen
>> <martin.petersen@...cle.com> wrote:
>>>>>>>> "Tejun" == Tejun Heo <tj@...nel.org> writes:
>>>>> In fact,we don't need libata to deal with hotplug in sas environment.
>>>>> So we can't run ata hotplug task when ata port is sas host.
>>> Tejun> Martin, can you please confirm whether the above is true.  If so,
>>> Tejun> I'll route the patch through libata w/ stable cc'd.
>>>
>>> Not exactly a libsas expert. James? Dan?
>> While it is true that libsas itself handles adding / removing devices
>> we have historically avoided this conflict because
>> ATA_PFLAG_SCSI_HOTPLUG is never set for libsas ata_ports.  So the bug
>> / behavior change is that  ATA_PFLAG_SCSI_HOTPLUG gets set in the
>> first place.  Ignoring it is a band-aid / not the real fix afaics.
> I see.  I'll hold off for now then.  Ding Xiang, can you find out
> where that flag is getting set?
>
> Thanks!
There are two places will set flag ATA_PFLAG_SCSI_HOTPLUG in libata-eh.c.
I think both places should  be protected. Here is the suggestion.
Thanks~

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 61dc7a9..2bee041 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1385,7 +1385,8 @@ void ata_eh_detach_dev(struct ata_device *dev)

         if (ata_scsi_offline_dev(dev)) {
                 dev->flags |= ATA_DFLAG_DETACHED;
-               ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
+               if (!(ap->pflags & ATA_FLAG_SAS_HOST))
+                       ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
         }

         /* clear per-dev EH info */
@@ -3299,7 +3300,8 @@ static int ata_eh_revalidate_and_attach(struct 
ata_link *link,
                 }

                 spin_lock_irqsave(ap->lock, flags);
-               ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
+               if (!(ap->pflags & ATA_FLAG_SAS_HOST))
+                       ap->pflags |= ATA_PFLAG_SCSI_HOTPLUG;
                 spin_unlock_irqrestore(ap->lock, flags);

                 /* new device discovered, configure xfermode */