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

From: dingxiang
Date: Wed Jun 22 2016 - 02:48:34 EST



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@xxxxxxxxxx> wrote:
"Tejun" == Tejun Heo <tj@xxxxxxxxxx> 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 */