Re: [PATCH] libxfs: detect zoned disks and prevent their raw use

[Dave Chinner <david@fromorbit.com>]

On Fri, Jun 15, 2018 at 01:50:11PM -0700, Luis R. Rodriguez wrote:
> Using raw zoned disks by filesystems requires special handling, only
> f2fs currently supports this. All other filesystems do not support
> dealing with zoned disks directly.
> 
> As such using raw zoned disks is not supported by XFS, to use them you
> need to use dm-zoned-tools, format them with dzadm, set the scheduler to
> deadline, and then setup a dmsetup with zoned type, and somehow set
> this up on every boot to live a semi-happy life for now.
> 
> Even if you use dmsetup on every boot, the zoned disk is still exposed,
> and a user may still think they have to run mkfs.xfs on it instead
> of the /dev/mapper/ disk, and then mount it by mistake.
> 
> In either case you may seem to believe your disk works and only eventually
> end up with alignmet issues and perhaps lose you data. For instance:
> 
> [10869.959501] device-mapper: zoned reclaim: (sda): Align zone 865 wp 28349 to 30842 (wp+2493) blocks failed -5
> [10870.014488] sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
> [10870.016137] sd 0:0:0:0: [sda] tag#0 Sense Key : Illegal Request [current]
> [10870.017696] sd 0:0:0:0: [sda] tag#0 Add. Sense: Unaligned write command
> 
> We have to prevent these mistakes by avoiding mkfs.xfs use on zoned disks.
> 
> Note that this not enough yet, if users are on old AHCI controllers,
> the disks may not be detected as zoned. More work through udev may be
> required to detect this situation old old parent PCI IDs for zoned
> disks, and then prevent their use somehow.
> 
> If you are stuck on using XFS there a udev rule out there [0], this is
> far from perfect, and not fully what we want done upstream on Linux
> distributions long term but it should at least help developers for now
> enjoy their shiny big fat zoned disks with XFS.
> 
> This check should help avoid having folks shoot themselves in the foot
> for now with zoned disks. If you make the mistake to use mkfs.xfs
> on a zoned disk, you will now get:
> 
>  # mkfs.xfs /dev/sda
> /dev/sda: zoned disk detected, refer to dm-zoned-tools for how to use with XFS

Shouldn't this code be put in libblkid() so it's available to all
filesystem tools, not just XFS?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com