[PATCH] btrfs: relocation: Output current relocation stage at btrfs_relocate_block_group()

[Qu Wenruo <wqu@suse.com>]

There are several reports of hanging relocation, populating the dmesg
with things like:
  BTRFS info (device dm-5): found 1 extents

The investigation is still on going, but will never hurt to output a
little more info.

This patch will also output the current relocation stage, making that
output something like:

  BTRFS info (device dm-5): balance: start -d -m -s
  BTRFS info (device dm-5): relocating block group 30408704 flags metadata|dup
  BTRFS info (device dm-5): found 2 extents at MOVE_DATA_EXTENTS stage
  BTRFS info (device dm-5): relocating block group 22020096 flags system|dup
  BTRFS info (device dm-5): found 1 extents at MOVE_DATA_EXTENTS stage
  BTRFS info (device dm-5): relocating block group 13631488 flags data
  BTRFS info (device dm-5): found 1 extents at MOVE_DATA_EXTENTS stage
  BTRFS info (device dm-5): found 1 extents at UPDATE_DATA_PTRS stage
  BTRFS info (device dm-5): balance: ended with status: 0

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/relocation.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index d897a8e5e430..b3bc5b571820 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4291,6 +4291,15 @@ static void describe_relocation(struct btrfs_fs_info *fs_info,
 		   block_group->start, buf);
 }
 
+static const char *stage_to_string(int stage)
+{
+	if (stage == MOVE_DATA_EXTENTS)
+		return "MOVE_DATA_EXTENTS";
+	if (stage == UPDATE_DATA_PTRS)
+		return "UPDATE_DATA_PTRS";
+	return "UNKNOWN";
+}
+
 /*
  * function to relocate all extents in a block group.
  */
@@ -4365,12 +4374,15 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 				 rc->block_group->length);
 
 	while (1) {
+		int finishes_stage;
+
 		mutex_lock(&fs_info->cleaner_mutex);
 		ret = relocate_block_group(rc);
 		mutex_unlock(&fs_info->cleaner_mutex);
 		if (ret < 0)
 			err = ret;
 
+		finishes_stage = rc->stage;
 		/*
 		 * We may have gotten ENOSPC after we already dirtied some
 		 * extents.  If writeout happens while we're relocating a
@@ -4396,8 +4408,8 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 		if (rc->extents_found == 0)
 			break;
 
-		btrfs_info(fs_info, "found %llu extents", rc->extents_found);
-
+		btrfs_info(fs_info, "found %llu extents at %s stage",
+			   rc->extents_found, stage_to_string(finishes_stage));
 	}
 
 	WARN_ON(rc->block_group->pinned > 0);
-- 
2.23.0