Re: [PATCH] btrfs: use btrfs_dev_name() helper to handle missing devices better

[David Sterba <dsterba@suse.cz>]

On Sun, Nov 13, 2022 at 09:32:07AM +0800, Qu Wenruo wrote:
> [BUG]
> If dev-replace failed to re-construct its data/metadata, the kernel
> message would be incorrect for the missing device:
> 
>  BTRFS info (device dm-1): dev_replace from <missing disk> (devid 2) to /dev/mapper/test-scratch2 started
>  BTRFS error (device dm-1): failed to rebuild valid logical 38862848 for dev (efault)
> 
> Note the above "dev (efault)" of the second line.
> While the first line is properly reporting "<missing disk>".
> 
> [CAUSE]
> Although dev-replace is using btrfs_dev_name(), the heavy lifting work
> is still done by scrub (scrub is reused by both dev-replace and regular
> scrub).
> 
> Unfortunately scrub code never uses btrfs_dev_name() helper, as it's
> only declared locally inside dev-replace.c.
> 
> [FIX]
> Fix the output by:
> 
> - Move the btrfs_dev_name() helper to volumes.h
> 
> - Use btrfs_dev_name() to replace open-coded rcu_str_defref() calls
>   Only zoned code is not touched, as I'm not familiar with degraded
>   zoned code.
> 
> Now the output looks pretty sane:
> 
>  BTRFS info (device dm-1): dev_replace from <missing disk> (devid 2) to /dev/mapper/test-scratch2 started
>  BTRFS error (device dm-1): failed to rebuild valid logical 38862848 for dev <missing disk>
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Added to misc-next, thanks.