From 5c596500e185a4bb8e18dc954227878f562bb7c9 Mon Sep 17 00:00:00 2001
From: Ralf Zerres <ralf.zerres@networkx.de>
Date: Fri, 9 Aug 2019 09:07:40 +0200
Subject: [PATCH] dsnap-sync: refine btrfs quota-group handling

- if qgroup usage is requested, need to check if it is already enabled
  if not, turn on this filesystem option an rescan for the given
  subvolume
- even rescanning and calculation the qgroup values might be faster
  for large subvolumes, than using plain 'du'
- just enable the qgroup usage for dsnap-sync runs. Upstream
  still encounters performance hits for regular production
  usage (v4.7: consult the wiki)
  this is controlled via enabling the global 'btrfs_quota_tmp' flag

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>
---
 bin/dsnap-sync | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/bin/dsnap-sync b/bin/dsnap-sync
index dbe7d12..ea08659 100755
--- a/bin/dsnap-sync
+++ b/bin/dsnap-sync
@@ -50,6 +50,7 @@ answer=no
 archive_type=full
 batch=0
 btrfs_quota=0
+btrfs_quota_tmp=1
 #btrfs_verbose_flag=--verbose
 btrfs_verbose_flag=
 color=0
@@ -1628,16 +1629,20 @@ run_backup () {
 		    # qgroup identifiers conform to level/id where level 0 is reserved to the qgroups associated with subvolumes
 		    snapper_source_snapshot_size=$(btrfs qgroup show -f --raw $snapper_source_snapshot 2>/dev/null \
 						       | awk 'FNR>2 {print $2}')
+                    if [ $? -eq 1 ]; then
+                        # subvolume is not configured for quota, (temporary?) enable that
+                        if [ $btrfs_quota_tmp -eq 1 ]; then
+                            btrfs quota enable $snapper_source_snapshot 2>/dev/null
+                            btrfs quota rescan -w $snapper_source_snapshot 2>/dev/null
+                            snapper_source_snapshot_size=$(btrfs qgroup show -f --raw $snapper_source_snapshot 2>/dev/null \
+                                                               | awk 'FNR>2 {print $2}')
+			fi
+		    fi
+
 		    if [ $verbose -ge 3 ]; then
 			printf "${MAGENTA}BTRFS qgroup show result: ${GREEN}'%s'\b${NO_COLOR}'%s'\n" \
 	    		       "$?" "$snapper_source_snapshot_size"
 		    fi
-		    #if [ $? -eq 1 ]; then
-		    # subvolume is not configured for quota, (temporary?) enable that
-		    #btrfs_quota_tmp=1
-		    #btrfs quota enable $snapper_source_snapshot 2>/dev/null
-		    #btrfs quota rescan -w $snapper_source_snapshot 2>/dev/null
-		    #fi
 
 		    # need to substitue btrfs 'x.yyGiB' suffix, since pv will need 'xG'
 		    if [ $snapper_source_snapshot_size -ge 1048576 ]; then
@@ -1650,7 +1655,7 @@ run_backup () {
 		    fi
 
 		    # should we disable quota usage again?
-		    #if [ $btrfs_quota_tmp -eq 1 ]; then btrfs quota disable $snapper_source_snapshot; fi
+		    if [ $btrfs_quota_tmp -eq 1 ]; then btrfs quota disable $snapper_source_snapshot; fi
 		else
 		    snapper_source_snapshot_size=$(du --one-file-system --summarize $snapper_source_snapshot 2>/dev/null \
 						       | awk -F ' ' '{print $1}')