btrfs: make block group flags in balance printks human-readable

They're not even documented anywhere, letting users with no recourse but
to RTFS.  It's no big burden to output the bitfield as words.

Also, display unknown flags as hex.
Signed-off-by: NAdam Borowski <kilobyte@angband.pl>
Tested-by: NHolger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -4332,6 +4332,45 @@ static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
 	return rc;
 }
 
+/*
+ * Print the block group being relocated
+ */
+static void describe_relocation(struct btrfs_fs_info *fs_info,
+				struct btrfs_block_group_cache *block_group)
+{
+	char buf[128];		/* prefixed by a '|' that'll be dropped */
+	u64 flags = block_group->flags;
+
+	/* Shouldn't happen */
+	if (!flags) {
+		strcpy(buf, "|NONE");
+	} else {
+		char *bp = buf;
+
+#define DESCRIBE_FLAG(f, d) \
+		if (flags & BTRFS_BLOCK_GROUP_##f) { \
+			bp += snprintf(bp, buf - bp + sizeof(buf), "|%s", d); \
+			flags &= ~BTRFS_BLOCK_GROUP_##f; \
+		}
+		DESCRIBE_FLAG(DATA,     "data");
+		DESCRIBE_FLAG(SYSTEM,   "system");
+		DESCRIBE_FLAG(METADATA, "metadata");
+		DESCRIBE_FLAG(RAID0,    "raid0");
+		DESCRIBE_FLAG(RAID1,    "raid1");
+		DESCRIBE_FLAG(DUP,      "dup");
+		DESCRIBE_FLAG(RAID10,   "raid10");
+		DESCRIBE_FLAG(RAID5,    "raid5");
+		DESCRIBE_FLAG(RAID6,    "raid6");
+		if (flags)
+			snprintf(buf, buf - bp + sizeof(buf), "|0x%llx", flags);
+#undef DESCRIBE_FLAG
+	}
+
+	btrfs_info(fs_info,
+		   "relocating block group %llu flags %s",
+		   block_group->key.objectid, buf + 1);
+}
+
 /*
  * function to relocate all extents in a block group.
  */
@@ -4388,9 +4427,7 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
 		goto out;
 	}
 
-	btrfs_info(extent_root->fs_info,
-		   "relocating block group %llu flags %llu",
-		   rc->block_group->key.objectid, rc->block_group->flags);
+	describe_relocation(extent_root->fs_info, rc->block_group);
 
 	btrfs_wait_block_group_reservations(rc->block_group);
 	btrfs_wait_nocow_writers(rc->block_group);