new executable: btrfs-truncate

1 files changed, 32 insertions, 0 deletions

diff --git a/src/btrfs-utils/btrfs-truncate b/src/btrfs-utils/btrfs-truncate
new file mode 100755
index 0000000..0075844
--- /dev/null
+++ b/src/btrfs-utils/btrfs-truncate
@@ -0,0 +1,32 @@
+#!/bin/sh
+[ "$(id -u)" = 0 ] || exec sudo "$0" "$@"
+
+btrfs_truncate()
+{
+  btrfs filesystem show --raw "$1" |
+    while read devid d size s used u path p
+    do
+      [ "$devid $size $used $path" = 'devid size used path' ] || continue
+
+      case "$p" in
+        /dev/loop*) dev=$(losetup -n -l -O back-file "$p") ;;
+        *) dev=$p ;;
+      esac
+
+      if [ -f "$dev" ]
+      then
+        [ "$s" = "$(stat -c %s "$dev")" ] || truncate -s "$s" "$dev" || break
+      fi
+    done
+}
+
+if [ $# = 0 ]
+then
+  echo 'Usage: $0 <btrfs mountpoint> [...]' >&2
+  exit 1
+fi
+
+for fs
+do
+  btrfs_truncate "$fs" || exit
+done