btrfs: use btrfs_dev_name() helper to handle missing devices better

[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_deref() calls
  Only zoned code is not touched, as I'm not familiar with degraded
  zoned code.

- Constify return value and parameter

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>

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 7ff0703ef3e4..82e49d985019 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -757,7 +757,7 @@ static int btrfsic_process_superblock_dev_mirror(
 			btrfs_info_in_rcu(fs_info,
 			"new initial S-block (bdev %p, %s) @%llu (%pg/%llu/%d)",
 				     superblock_bdev,
-				     rcu_str_deref(device->name), dev_bytenr,
+				     btrfs_dev_name(device), dev_bytenr,
 				     dev_state->bdev, dev_bytenr,
 				     superblock_mirror_num);
 		list_add(&superblock_tmp->all_blocks_node,