[PATCH v2] btrfs: make block group flags in balance printks human-readable

[Adam Borowski <kilobyte@angband.pl>]

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: Adam Borowski <kilobyte@angband.pl>
---
 fs/btrfs/relocation.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index c4af0cd..b5d2a00 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4333,6 +4333,42 @@ static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
 }
 
 /*
+ * explain bit flags, prefixed by a '|' that'll be dropped
+ */
+static char *describe_block_group_flags(char *buf, u64 flags)
+{
+#define BUF_SIZE 128
+	char *buf0 = buf = kmalloc(BUF_SIZE, GFP_NOFS);
+
+	if (!buf)
+		return 0;
+
+	if (!flags) {
+		strcpy(buf, "|NONE");
+		return buf0;
+	}
+#define DESCRIBE_FLAG(f, d) \
+		if (flags & BTRFS_BLOCK_GROUP_##f) { \
+			buf += snprintf(buf, buf0 - buf + BUF_SIZE, "|%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)
+		buf += snprintf(buf, buf0 - buf + BUF_SIZE, "|0x%llx", flags);
+	return buf0;
+#undef DESCRIBE_FLAG
+#undef BUF_SIZE
+}
+
+/*
  * function to relocate all extents in a block group.
  */
 int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
@@ -4344,6 +4380,7 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
 	int ret;
 	int rw = 0;
 	int err = 0;
+	char *flags_str;
 
 	rc = alloc_reloc_control(fs_info);
 	if (!rc)
@@ -4388,9 +4425,19 @@ 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);
+	if ((flags_str = describe_block_group_flags(flags_str,
+						   rc->block_group->flags))) {
+		btrfs_info(extent_root->fs_info,
+			   "relocating block group %llu flags %s",
+			   rc->block_group->key.objectid,
+			   flags_str+1);
+		kfree(flags_str);
+	} else {
+		btrfs_info(extent_root->fs_info,
+			   "relocating block group %llu flags %llx",
+			   rc->block_group->key.objectid,
+			   rc->block_group->flags);
+	}
 
 	btrfs_wait_block_group_reservations(rc->block_group);
 	btrfs_wait_nocow_writers(rc->block_group);
-- 
2.10.2