My device has errors injected:
# ndctl inject-error --status namespace2.0{
"badblocks":[
{
"block":35000,
"count":10
}
]
}
No problem reading from the bad offsets:
# dd if=/dev/pmem2 of=/tmp/pmem_out bs=512 count=10 skip=35000
10+0 records in
10+0 records out
5120 bytes (5.1 kB) copied, 0.000108226 s, 47.3 MB/s
Kernel doesn't know of the badblocks yet so this should have resulted in sigbus
for dd:
# cat /sys/block/pmem2/badblocks#
I dont have mcelog daemon running but there is no error in /var/log/messages
for pmem device. Is there some setting/config that I am missing ?
-KK
On Thursday, January 3, 2019, 1:39:44 PM EST, Verma, Vishal L
<[email protected]> wrote:
On Thu, 2019-01-03 at 17:13 +0000, Kamal Kakri wrote:
> I am playing around with ndctl inject-error and have a few questions
> around the behavior of the application when an error occurs.
> After successfully injecting error with --no-notify, I am able to
> read and write to the namespace device with no problems. For e.g.:
>
> # ndctl inject-error --block=35000 --count=10 --no-notify
> namespace2.0{
> "dev":"namespace2.0",
> "mode":"raw",
> "size":17179869184,
> "blockdev":"pmem2"
> }
>
>
> # dd if=/dev/pmem2 of=/tmp/pmem-dump bs=512 count=10 seek=35000 oflag=direct
I think you want 'skip=35000' here instead of seek= to read from that
offset in the input.
> 10+0 records in
> 10+0 records out
> 5120 bytes (5.1 kB) copied, 0.0128088 s, 400 kB/s
>
> # pwd
> /sys/block/pmem2
> # cat badblocks
> # ----------> empty badblock list
With --no-notify badblocks is expected to be empty, as ACPI will not
notify the OS of new errors.
>
>
> [Question] Shouldn't my "dd" get a SIGBUS (default machine-check
> handling) when it encounters badblocks that its not aware of (no-
> notify) ?
Yes it should - I'd be curious to see if you still don't get a machine
check with the seek/skip fix above.
>
>
> I tried to do both reading and writing to badblocks and things just
> work. If I scrub my nvdimm's (ndctl start-scrub) and the badblocks
> show up in device badblock list (/sys/block/pmem/badblocks) but dd
> can still work and writing the blocks clears out the badblock list:
> # cat /sys/block/pmem2/badblocks35000 10
>
> # dd if=/dev/zero of=/dev/pmem2 bs=512 count=10 seek=35000
> oflag=direct
> 10+0 records in
> 10+0 records out
Writing with O_DIRECT is the canonical way to clear errors - what you
might see here is a corrected machine check notification in your kernel
logs (CMCI), but that is just a notification that the platform has
handled the error and no action is required.
-Vishal
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