dd: vm_fault: pager read error

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dd: vm_fault: pager read error

grarpamp
Here is a report of a repeatable unrecoverable problem.

11.0 release amd64 r306420

kern.geom.debugflags=0 (unmodified)

# dd if=/dev/zero of=/dev/ada0s1 seek=2048 count=1 bs=1m
1+0 records in
1+0 records out
1048576 bytes transferred

# reboot
# <reboot: Device not configured>
The same goes for any other uncached access to the
filesystem in ada0s1a (Note: / is on s1a, dd occurs past
that), ie all first use of commands that read disk.

Repeating scrolling the console...
"
vnode_pager_generic_getpages_done: I/O read error 5
vm_fault: pager read error, pid 1 (init)
"

Requires HW reset button, then after system comes back
up, all layout, filesystems, and data are fine.

Repeatable every time.

Also,

# echo '<random_string>' | dd of=/dev/ada0s1 seek=2048 count=1 bs=1m conv=sync

does get written to disk and is readable upon reboot,

# dd if=/dev/ada0s1 skip=2048 count=1 bs=1m
# <random_string>

wherein that read does not trigger the fault,
only the write of the string does.

All the layout offsets and sizes add up sequentially, no overlap,
the relavant portions are below, disk is <~= 250G,
gpart, fdisk, boot0cfg, bsdlabel all concur without error,
and were done with the live release tool versions.

What am I overlooking, or is this kernel behaviour a bug?

=>       63        x    ada0  MBR  (XG)
         63          1          - free -  (512B)
         64    8388608  ada0s1  freebsd  [active]  (4.0G)
    8388672  109051904  ada0s2  freebsd  (52G)

=>      0  8388608   ada0s1  BSD  (4.0G)
        0  4194304  ada0s1a  freebsd-ufs  (2.0G) /
  4194304  4194304           - free -  (2.0G)
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Re: dd: vm_fault: pager read error

Eugene Grosbein-10
09.10.2017 1:23, grarpamp пишет:

> Here is a report of a repeatable unrecoverable problem.
>
> 11.0 release amd64 r306420
>
> kern.geom.debugflags=0 (unmodified)
>
> # dd if=/dev/zero of=/dev/ada0s1 seek=2048 count=1 bs=1m
> 1+0 records in
> 1+0 records out
> 1048576 bytes transferred
>
> # reboot
> # <reboot: Device not configured>

The problem is known and already fixed. You should upgrade.


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Re: dd: vm_fault: pager read error

grarpamp
On Sun, Oct 8, 2017 at 3:05 PM, Eugene Grosbein <[hidden email]> wrote:
> The problem is known and already fixed. You should upgrade.

Was there a ticket and revision number to look into that?
Because this issue is still present in 11.1 and r324300.

When booting either from usb...

- Mounting ada0s1a read-only on /mnt, and giving the same
dd, still produces "Device not configured" upon an ls -R /mnt.
A umount clears that condition. Repeat.

- After triggering it read-only, but not unmounting to clear
it, a mount -uw panics the box.

- Giving the dd in unmounted state appears to be ok.


Another issue:

debugflags=16, manpage say 'allow[s]...write[ing]...sectors... to
mounted [read-write?] disk [the aforesaid mounted partition on it?]".
The manpage is unclear there. Also geom(8) does not display
that actual rank status info, ie: "Rank 1 provider". IMO, 16 should
"allow [all] foot shooting".
So mode 16 appears to be broken because the dd is denied,
even though the dd is NOT writing to the read-write mounted
s1a partition itself (which should be allowed even if it were),
but is seeking over past it.
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Re: dd: vm_fault: pager read error

Eugene Grosbein-10
10.10.2017 15:06, grarpamp пишет:
> On Sun, Oct 8, 2017 at 3:05 PM, Eugene Grosbein <[hidden email]> wrote:
>> The problem is known and already fixed. You should upgrade.
>
> Was there a ticket and revision number to look into that?
> Because this issue is still present in 11.1 and r324300.

It was meant to be https://svnweb.freebsd.org/base?view=revision&sortby=date&revision=320566
If you are sure running kernel after 320566, you should fill a PR.

Please be more specific of your configuration, including full 'gpart show' output,
list of mounted file systems, uname -K output, exact text of commands and system responces.


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Re: dd: vm_fault: pager read error

grarpamp
In reply to this post by grarpamp
> Eugene Grosbein <[hidden email]> wrote:
>> Was there a ticket and revision number to look into that?
>> Because this issue is still present in 11.1 and r324300.

> It was meant to be
> https://svnweb.freebsd.org/base?view=revision&sortby=date&revision=320566

Found the thread... seems the same "Device not configured" problem,
just triggered differently by different users...
https://lists.freebsd.org/pipermail/freebsd-stable/2017-June/thread.html

I think 320566 may have quashed the two pager messages bits
(I don't seem to get them anymore), but the "Device not configured"
issue people observed is still there.

> If you are sure running kernel after 320566

Both 11.1R (r321309) and r324300 (same as snapshot) are after that.

> you should fill a PR.

Assuming there's not already one.
Then one for this issue when cleaned up.
And probably another for the geom.debugflags footshooting semantics.

Also I need to capture that mount -uw panic but have to look up again
the sysctl to prevent instant reboot / leave it onscreen or to debugger.
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Re: dd: vm_fault: pager read error

grarpamp
Eugene Grosbein <[hidden email]> wrote:
> you should fill a PR.

# LOR Panic in disk access
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222948

As above, filed with script for easy repeat.

Earlier I put some emails leading up to ticket
that may be related:
current@ regarding Subject: LOR
stable@ fs@ regarding Subject: dd

Thanks.
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