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>

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,

fs/btrfs/dev-replace.c

@@ -18,7 +18,6 @@
 #include "volumes.h"
 #include "async-thread.h"
 #include "check-integrity.h"
-#include "rcu-string.h"
 #include "dev-replace.h"
 #include "sysfs.h"
 #include "zoned.h"
@@ -451,14 +450,6 @@ out:
 	return ret;
 }
 
-static char* btrfs_dev_name(struct btrfs_device *device)
-{
-	if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
-		return "<missing disk>";
-	else
-		return rcu_str_deref(device->name);
-}
-
 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 				    struct btrfs_device *src_dev)
 {
@@ -674,7 +665,7 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 		      "dev_replace from %s (devid %llu) to %s started",
 		      btrfs_dev_name(src_device),
 		      src_device->devid,
-		      rcu_str_deref(tgt_device->name));
+		      btrfs_dev_name(tgt_device));
 
 	/*
 	 * from now on, the writes to the srcdev are all duplicated to
@@ -933,7 +924,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 				 "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 				 btrfs_dev_name(src_device),
 				 src_device->devid,
-				 rcu_str_deref(tgt_device->name), scrub_ret);
+				 btrfs_dev_name(tgt_device), scrub_ret);
 error:
 		up_write(&dev_replace->rwsem);
 		mutex_unlock(&fs_info->chunk_mutex);
@@ -951,7 +942,7 @@ error:
 			  "dev_replace from %s (devid %llu) to %s finished",
 			  btrfs_dev_name(src_device),
 			  src_device->devid,
-			  rcu_str_deref(tgt_device->name));
+			  btrfs_dev_name(tgt_device));
 	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 	tgt_device->devid = src_device->devid;
 	src_device->devid = BTRFS_DEV_REPLACE_DEVID;

fs/btrfs/disk-io.c

@@ -3944,7 +3944,7 @@ static void btrfs_end_super_write(struct bio *bio)
 		if (bio->bi_status) {
 			btrfs_warn_rl_in_rcu(device->fs_info,
 				"lost page write due to IO error on %s (%d)",
-				rcu_str_deref(device->name),
+				btrfs_dev_name(device),
 				blk_status_to_errno(bio->bi_status));
 			ClearPageUptodate(page);
 			SetPageError(page);

fs/btrfs/extent-tree.c

@@ -6048,7 +6048,7 @@ static int btrfs_trim_free_extents(struct btrfs_device *device, u64 *trimmed)
 			btrfs_warn_in_rcu(fs_info,
 "ignoring attempt to trim beyond device size: offset %llu length %llu device %s device size %llu",
 					  start, end - start + 1,
-					  rcu_str_deref(device->name),
+					  btrfs_dev_name(device),
 					  device->total_bytes);
 			mutex_unlock(&fs_info->chunk_mutex);
 			ret = 0;

fs/btrfs/extent_io.c

@@ -611,8 +611,7 @@ static int repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
 
 	btrfs_info_rl_in_rcu(fs_info,
 		"read error corrected: ino %llu off %llu (dev %s sector %llu)",
-				  ino, start,
-				  rcu_str_deref(dev->name), sector);
+			     ino, start, btrfs_dev_name(dev), sector);
 	ret = 0;
 
 out_bio_uninit:

fs/btrfs/ioctl.c

@@ -1228,7 +1228,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 	if (ret == 0 && new_size != old_size)
 		btrfs_info_in_rcu(fs_info,
 			"resize device %s (devid %llu) from %llu to %llu",
-			rcu_str_deref(device->name), device->devid,
+			btrfs_dev_name(device), device->devid,
 			old_size, new_size);
 out_finish:
 	btrfs_exclop_finish(fs_info);
@@ -2860,7 +2860,7 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
 	di_args->total_bytes = btrfs_device_get_total_bytes(dev);
 	memcpy(di_args->uuid, dev->uuid, sizeof(di_args->uuid));
 	if (dev->name) {
-		strncpy(di_args->path, rcu_str_deref(dev->name),
+		strncpy(di_args->path, btrfs_dev_name(dev),
 				sizeof(di_args->path) - 1);
 		di_args->path[sizeof(di_args->path) - 1] = 0;
 	} else {

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;
 	}

fs/btrfs/super.c

@@ -2336,7 +2336,7 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
 	 * the end of RCU grace period.
 	 */
 	rcu_read_lock();
-	seq_escape(m, rcu_str_deref(fs_info->fs_devices->latest_dev->name), " \t\n\\");
+	seq_escape(m, btrfs_dev_name(fs_info->fs_devices->latest_dev), " \t\n\\");
 	rcu_read_unlock();
 
 	return 0;

fs/btrfs/volumes.c

@@ -941,7 +941,7 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 			}
 			btrfs_info_in_rcu(NULL,
 	"devid %llu device path %s changed to %s scanned by %s (%d)",
-					  devid, rcu_str_deref(device->name),
+					  devid, btrfs_dev_name(device),
 					  path, current->comm,
 					  task_pid_nr(current));
 		}
@@ -2101,7 +2101,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info,
 	if (btrfs_pinned_by_swapfile(fs_info, device)) {
 		btrfs_warn_in_rcu(fs_info,
 		  "cannot remove device %s (devid %llu) due to active swapfile",
-				  rcu_str_deref(device->name), device->devid);
+				  btrfs_dev_name(device), device->devid);
 		return -ETXTBSY;
 	}
 
@@ -6827,7 +6827,7 @@ static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
 	btrfs_debug_in_rcu(dev->fs_info,
 	"%s: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
 		__func__, bio_op(bio), bio->bi_opf, bio->bi_iter.bi_sector,
-		(unsigned long)dev->bdev->bd_dev, rcu_str_deref(dev->name),
+		(unsigned long)dev->bdev->bd_dev, btrfs_dev_name(dev),
 		dev->devid, bio->bi_iter.bi_size);
 
 	btrfsic_check_bio(bio);
@@ -7908,7 +7908,7 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 	if (ret < 0) {
 		btrfs_warn_in_rcu(fs_info,
 			"error %d while searching for dev_stats item for device %s",
-			      ret, rcu_str_deref(device->name));
+				  ret, btrfs_dev_name(device));
 		goto out;
 	}
 
@@ -7919,7 +7919,7 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 		if (ret != 0) {
 			btrfs_warn_in_rcu(fs_info,
 				"delete too small dev_stats item for device %s failed %d",
-				      rcu_str_deref(device->name), ret);
+					  btrfs_dev_name(device), ret);
 			goto out;
 		}
 		ret = 1;
@@ -7933,7 +7933,7 @@ static int update_dev_stat_item(struct btrfs_trans_handle *trans,
 		if (ret < 0) {
 			btrfs_warn_in_rcu(fs_info,
 				"insert dev_stats item for device %s failed %d",
-				rcu_str_deref(device->name), ret);
+				btrfs_dev_name(device), ret);
 			goto out;
 		}
 	}
@@ -7998,7 +7998,7 @@ void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index)
 		return;
 	btrfs_err_rl_in_rcu(dev->fs_info,
 		"bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
-			   rcu_str_deref(dev->name),
+			   btrfs_dev_name(dev),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
 			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
@@ -8018,7 +8018,7 @@ static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
 
 	btrfs_info_in_rcu(dev->fs_info,
 		"bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
-	       rcu_str_deref(dev->name),
+	       btrfs_dev_name(dev),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
 	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),

fs/btrfs/volumes.h

@@ -12,6 +12,7 @@
 #include "async-thread.h"
 #include "messages.h"
 #include "disk-io.h"
+#include "rcu-string.h"
 
 #define BTRFS_MAX_DATA_CHUNK_SIZE	(10ULL * SZ_1G)
 
@@ -770,6 +771,14 @@ static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
 	atomic_inc(&dev->dev_stats_ccnt);
 }
 
+static inline const char *btrfs_dev_name(const struct btrfs_device *device)
+{
+	if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
+		return "<missing disk>";
+	else
+		return rcu_str_deref(device->name);
+}
+
 void btrfs_commit_device_sizes(struct btrfs_transaction *trans);
 
 struct list_head * __attribute_const__ btrfs_get_fs_uuids(void);