disk "flipped" - a known problem?

[Steven Hartland]

----- Original Message ----- 
From: "Jeremy Chadwick" <jdc at koitsu.org>
To: <freebsd-fs at freebsd.org>
Cc: <mav at freebsd.org>; <avg at freebsd.org>
Sent: Monday, January 21, 2013 10:16 PM
Subject: Re: disk "flipped" - a known problem?


> (Please keep me CC'd as I am not subscribed)
> 
> WRT this:
> 
> http://lists.freebsd.org/pipermail/freebsd-fs/2013-January/016197.html
> 
> I can reproduce the first problem 100% of the time on my home system
> here.  I can provide hardware specs if needed, but the important part is
> that I'm using RELENG_9 / r245697, the controller is an ICH9R in AHCI
> mode (and does not share an IRQ), hot-swap bays are in use, and I'm
> using ahci.ko.
> 
> I also want to make this clear to Andriy: I'm not saying "there's a
> problem with your disk".  In my case, I KNOW there's a problem with the
> disk (that's the entire point to my tests! :-) ).
> 
> In my case the disk is a WD Raptor (150GB, circa 2006) that has a very
> badly-designed firmware that goes completely catatonic when encountering
> certain sector-level conditions.  That's not the problem though -- the
> problem is with FreeBSD apparently getting confused as to the internal
> state of its devices after a device falls off the bus and comes back.
> Explanation:
> 
> 1. System powered off; disk is attached; system powered on, shows up as
> ada5.  Can communicate with device in every way (the way I tend to test
> simple I/O is to use "smartctl -a /dev/ada5").  This disk has no
> filesystems or other "stuff" on it -- it's just a raw disk, so I believe
> the g_wither_washer oddity does not apply in this situation.
> 
> 2. "dd if=/dev/zero of=/dev/ada5 bs=64k"
> 
> 3. Drive hits a bad sector which it cannot remap/deal with.  Drive
> firmware design flaw results in drive becoming 100% stuck trying to
> re-read the sector and work out internal decisions to do remapping or
> not.  Drive audibly clicking during this time (not actuator arm being
> reset to track 0 noise; some other mechanical issue).  Due to firmware
> issue, drive remains in this state indefinitely.
> 
> 4. FreeBSD CAM reports repeated WRITE_FPDMA_QUEUED (i.e. writes using NCQ)
> errors every 30 seconds (kern.cam.ada.default_timeout), for a total of 5
> times (kern.cam.da.retry_count+1).
> 
> 5. FreeBSD spits out similar messages you see; retries exhausted,
> cam_periph_alloc error, and devfs claims device removal.
> 
> 6. Drive is still catatonic of course.  Only way to reset the drive is
> to power-cycle it.  Drive removed from hot-swap bay, let sit for 20
> seconds, then is reinserted.
> 
> 7. FreeBSD sees the disk reappear, shows up much like it did during #1,
> except...
> 
> 8. "smartctl -a /dev/ada5" claims no such device or unknown device type
> (I forget which).  "ls -l /dev/ada5" shows an entry.  "camcontrol
> devlist" shows the disk on the bus, yet I/O does not work.  If I
> remember right, re-attempting the dd command returns some error (I
> forget which).
> 
> 9. "camcontrol rescan all" stalls for quite some time when trying to
> communicate with entry 5, but eventually does return (I think with some
> error).  camcontrol reset all" works without a hitch.  "camcontrol
> devlist" during this time shows the same disk on ada5 (which to me means
> ATA IDENTIFY, i.e. vendor strings, etc. are reobtained somehow, meaning
> I/O works at some level).
> 
> 10. System otherwise works fine, but the only way to bring back
> usability of ada5 is to reboot ("shutdown -r now").
> 
> To me, this looks like FreeBSD at some layer within the kernel (or some
> driver (I don't know which)) is internally confused about the true state
> of things.
> 
> Alexander, do you have any ideas?
> 
> I can enable CAM debugging (I do use options CAMDEBUG so I can toggle
> this with camcontrol) as well as take notes and do a full step-by-step
> diagnosis (along with relevant kernel output seen during each phase) if
> that would help you.  And I can test patches but not against -CURRENT
> (will be a cold day in hell before I run that, sorry).
> 
> Let me know, time permitting.  :-)

Do you have a controller which not ata based you can test this on e.g.
mps as this may help identify if the issue is ata specific or more
generic. If you have the messages log for above scenario that also might
help to track down the problem.

It does, as you say, sound like something isn't being cleaned up properly
which might be confirmed by adding a printf just inside cam_periph_alloc's
    if ((periph = cam_periph_find(path, name)) != NULL) {

    Regards
    Steve

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