btrfs: qgroup: More meaningful qgroup_rescan_init error message

Error message from qgroup_rescan_init() mostly looks like:

------
BTRFS info (device nvme0n1p1): qgroup_rescan_init failed with -115
------

Which is far from meaningful, and sometimes confusing as for above -EINPROGRESS it's mostly (despite the init race) harmless, but sometimes it can also indicates problem if return value is -EINVAL.

Change it to some more meaningful messages like:

------
BTRFS info (device nvme0n1p1): qgroup rescan is already in progress
------

And

------
BTRFS err(device nvme0n1p1): qgroup_rescan_init failed, qgroup is not enabled
------

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/qgroup.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

fs/btrfs/qgroup.c +19 -15

index ec2339a49ec3..a5742e9e9a14 100644
@@ -2760,26 +2760,37 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
 {
 	int ret = 0;
 
-	if (!init_flags &&
-	    (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) ||
-	     !(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))) {
-		ret = -EINVAL;
-		goto err;
+	if (!init_flags) {
+		/* we're resuming qgroup rescan at mount time */
+		if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN))
+			btrfs_err(fs_info, "%s failed, qgroup is not enabled",
+				  __func__);
+		else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
+			btrfs_err(fs_info,
+				  "%s failed, qgroup rescan is not queued",
+				  __func__);
+		return -EINVAL;
 	}
 
 	mutex_lock(&fs_info->qgroup_rescan_lock);
 	spin_lock(&fs_info->qgroup_lock);
 
 	if (init_flags) {
-		if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
+		if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
+			btrfs_info(fs_info,
+				   "qgroup rescan is already in progress");
 			ret = -EINPROGRESS;
-		else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
+		} else if (!(fs_info->qgroup_flags &
+			     BTRFS_QGROUP_STATUS_FLAG_ON)) {
+			btrfs_err(fs_info, "%s failed, qgroup is not enabled",
+				  __func__);
 			ret = -EINVAL;
+		}
 
 		if (ret) {
 			spin_unlock(&fs_info->qgroup_lock);
 			mutex_unlock(&fs_info->qgroup_rescan_lock);
-			goto err;
+			return ret;
 		}
 		fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
 	}

@@ -2798,13 +2809,6 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
 	btrfs_init_work(&fs_info->qgroup_rescan_work,
 			btrfs_qgroup_rescan_helper,
 			btrfs_qgroup_rescan_worker, NULL, NULL);
-
-	if (ret) {
-err:
-		btrfs_info(fs_info, "qgroup_rescan_init failed with %d", ret);
-		return ret;
-	}
-
 	return 0;
 }
 

Error message from qgroup_rescan_init() mostly looks like:

------
BTRFS info (device nvme0n1p1): qgroup_rescan_init failed with -115
------

Which is far from meaningful, and sometimes confusing as for above -EINPROGRESS it's mostly (despite the init race) harmless, but sometimes it can also indicates problem if return value is -EINVAL.

Change it to some more meaningful messages like:

------
BTRFS info (device nvme0n1p1): qgroup rescan is already in progress
------

And

------
BTRFS err(device nvme0n1p1): qgroup_rescan_init failed, qgroup is not enabled
------

Signed-off-by Qu Wenruo <[email protected]>

---
 fs/btrfs/qgroup.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

fs/btrfs/qgroup.c +0 -0

index ec2339a49ec3..a5742e9e9a14 100644
@@ -2760,26 +2760,37 @@ qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
 {
 	int ret = 0;