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, 9 insertions, 11 deletions

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 288a97992aa4..0ce5b773867f 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -17,7 +17,6 @@
 #include "extent_io.h"
 #include "dev-replace.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "raid56.h"
 #include "block-group.h"
 #include "zoned.h"
@@ -877,7 +876,7 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 num_bytes,
 		btrfs_warn_in_rcu(fs_info,
 "%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu, length %u, links %u (path: %s)",
 				  swarn->errstr, swarn->logical,
-				  rcu_str_deref(swarn->dev->name),
+				  btrfs_dev_name(swarn->dev),
 				  swarn->physical,
 				  root, inum, offset,
 				  fs_info->sectorsize, nlink,
@@ -891,7 +890,7 @@ err:
 	btrfs_warn_in_rcu(fs_info,
 			  "%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu: path resolving failed with ret=%d",
 			  swarn->errstr, swarn->logical,
-			  rcu_str_deref(swarn->dev->name),
+			  btrfs_dev_name(swarn->dev),
 			  swarn->physical,
 			  root, inum, offset, ret);
 
@@ -922,8 +921,7 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 	/* Super block error, no need to search extent tree. */
 	if (sblock->sectors[0]->flags & BTRFS_EXTENT_FLAG_SUPER) {
 		btrfs_warn_in_rcu(fs_info, "%s on device %s, physical %llu",
-			errstr, rcu_str_deref(dev->name),
-			sblock->physical);
+			errstr, btrfs_dev_name(dev), sblock->physical);
 		return;
 	}
 	path = btrfs_alloc_path();
@@ -954,7 +952,7 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 			btrfs_warn_in_rcu(fs_info,
 "%s at logical %llu on dev %s, physical %llu: metadata %s (level %d) in tree %llu",
 				errstr, swarn.logical,
-				rcu_str_deref(dev->name),
+				btrfs_dev_name(dev),
 				swarn.physical,
 				ref_level ? "node" : "leaf",
 				ret < 0 ? -1 : ref_level,
@@ -1377,7 +1375,7 @@ corrected_error:
 			spin_unlock(&sctx->stat_lock);
 			btrfs_err_rl_in_rcu(fs_info,
 				"fixed up error at logical %llu on dev %s",
-				logical, rcu_str_deref(dev->name));
+				logical, btrfs_dev_name(dev));
 		}
 	} else {
 did_not_correct_error:
@@ -1386,7 +1384,7 @@ did_not_correct_error:
 		spin_unlock(&sctx->stat_lock);
 		btrfs_err_rl_in_rcu(fs_info,
 			"unable to fixup (regular) error at logical %llu on dev %s",
-			logical, rcu_str_deref(dev->name));
+			logical, btrfs_dev_name(dev));
 	}
 
 out:
@@ -2332,14 +2330,14 @@ static void scrub_missing_raid56_worker(struct work_struct *work)
 		spin_unlock(&sctx->stat_lock);
 		btrfs_err_rl_in_rcu(fs_info,
 			"IO error rebuilding logical %llu for dev %s",
-			logical, rcu_str_deref(dev->name));
+			logical, btrfs_dev_name(dev));
 	} else if (sblock->header_error || sblock->checksum_error) {
 		spin_lock(&sctx->stat_lock);
 		sctx->stat.uncorrectable_errors++;
 		spin_unlock(&sctx->stat_lock);
 		btrfs_err_rl_in_rcu(fs_info,
 			"failed to rebuild valid logical %llu for dev %s",
-			logical, rcu_str_deref(dev->name));
+			logical, btrfs_dev_name(dev));
 	} else {
 		scrub_write_block_to_dev_replace(sblock);
 	}
@@ -4303,7 +4301,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
 		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 		btrfs_err_in_rcu(fs_info,
 			"scrub on devid %llu: filesystem on %s is not writable",
-				 devid, rcu_str_deref(dev->name));
+				 devid, btrfs_dev_name(dev));
 		ret = -EROFS;
 		goto out;
 	}