Re: raid1 narrow_write_error with 4K disks, sd "bad block number requested" messages

[NeilBrown <neilb@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 1942 bytes --]

On Wed, 28 Jan 2015 10:29:46 -0500 Nate Dailey <nate.dailey@stratus.com>
wrote:

> I'm writing about something that appears to be an issue with raid1's 
> narrow_write_error, particular to non-512-byte-sector disks. Here's what 
> I'm doing:
> 
> - 2 disk raid1, 4K disks, each connected to a different SAS HBA
> - mount a filesystem on the raid1, run a test that writes to it
> - remove one of the SAS HBAs (echo 1 > 
> /sys/bus/pci/devices/0000\:45\:00.0/remove)
> 
> At this point, writes fail and narrow_write_error breaks them up and 
> retries, one sector at a time. But these are 512-byte sectors, and sd 
> doesn't like it:
> 
> [ 2645.310517] sd 3:0:1:0: [sde] Bad block number requested
> [ 2645.310610] sd 3:0:1:0: [sde] Bad block number requested
> [ 2645.310690] sd 3:0:1:0: [sde] Bad block number requested
> ...
> 
> There appears to be no real harm done, but there can be a huge number of 
> these messages in the log.
> 
> I can avoid this by disabling bad block tracking, but it looks like 
> maybe the superblock's bblog_shift is intended to address this exact 
> issue. However, I don't see a way to change it. Presumably this is 
> something mdadm should be setting up? I don't see bblog_shift ever set 
> to anything other than 0.
> 
> This is on a RHEL 7.1 kernel, version 3.10.0-221.el7. I took a look at 
> upstream sd and md changes and nothing jumps out at me that would have 
> affected this (but I have not tested to see if the bad block messages do 
> or do not happen on an upstream kernel).
> 
> I'd appreciate any advice re: how to handle this. Thanks!

Thanks for the report.

narrow_write_error() should use bdev_logical_block_size() and round up to
that.
Possibly mdadm should get the same information and set bblog_shift
accordingly when creating a bad block log.

I've made a note to fix that, but I'm happy to review  patches too :-)

thanks,
NeilBrown


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 811 bytes --]