optimize away .5 seconds

diff --git a/filesystem/usr/local/bin/mount-latest-subvol b/filesystem/usr/local/bin/mount-latest-subvol
index 376b0d8ed35a94d37c165a6e5360f2f8c4d87bc5..2cf48d4c5d4d39a9b1ee0dd7e5bb9d669086a8da 100755 (executable)
--- a/filesystem/usr/local/bin/mount-latest-subvol
+++ b/filesystem/usr/local/bin/mount-latest-subvol
@@ -129,15 +129,15 @@ mapper-dev() {
 }
 
 
-# Input vars: $d, eg: /a
+# Input vars: $vol, eg:a
 #
-# Output vars: $root_dir, eg: /mnt/root
+# Output vars: $root_dirs[$vol], eg: root_dir[a]=/mnt/root
 #
 # Note: code-organizational only function.
 get-btrfs-root-mountpoint() {
   local dev devx
   ### this is duplicated in check-subvol-stale
-  dev=$(sed -rn "s,^\s*([^#]\S*)\s+$d\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
+  dev=$(sed -rn "s,^\s*([^#]\S*)\s+/$vol\s.*,\1,p" /etc/fstab /etc/mtab|head -n1)
   # example dev: /dev/mapper/crypt-vgDISK_BY_ID_NAME-root
   d dev=$dev
   # $devx are the devices of the btrfs filesystem. they include $dev.
@@ -160,9 +160,10 @@ get-btrfs-root-mountpoint() {
     echo "$0: error could not find root subvol mount for $dev" >&2
     exit 1
   fi
+  root_dirs[$vol]=$root_dir
 }
 
-# Input vars: $vol, $root_dir (from get-btrfs-root-mountpoint)
+# Input vars: $vol, $root_dir
 # Note: we cd $root_dir.
 expire-leaf-vols() {
   local leaf_vols count leaf_limit_time  leaf_new_limit_time leaf
@@ -189,7 +190,7 @@ expire-leaf-vols() {
 #
 # Silently give up if $1 is not a child of a btrbk subvol.
 #
-# Input vars: $vol $root_dir (from get-btrfs-root-mounts)
+# Input vars: $vol $root_dir
 dedupe-btrbk() {
   local parentid subvol parent_sub i lines tmpstr
   local -a bsubs
@@ -228,7 +229,7 @@ dedupe-btrbk() {
 
 # Maybe move volume to leaf.
 #
-# Input vars: $vol, $root_dir (from get-btrfs-root-mountpoint)
+# Input vars: $vol, $root_dir
 #
 # Note: we cd $root_dir.
 mv-vol-to-leaf() {
@@ -419,6 +420,7 @@ prune-vols() {
     ##### end #####
 
     pruned_vols+=("$vol")
+    get-btrfs-root-mountpoint
   done
 }
 
@@ -426,15 +428,15 @@ prune-vols() {
 # Find and fix the case where a bind mount's original source directory
 # got remounted with a different filesystem.
 #
-# Input vars: ${pruned_vols[@]}
+# Input vars: ${pruned_vols[@]} ${root_dirs[@]}
 #
-# Set leftover vars: $root_dir
+# Leftover vars: $root_dir
 mount-mismatch-fix() {
   local vol vol_id mp mp_id found_mismatch
   local -a to_umount
   for vol in ${pruned_vols[@]}; do
     set-d-binds
-    get-btrfs-root-mountpoint
+    root_dir=${root_dirs[$vol]}
     found_mismatch=false
     vol_id=$(stat -c%d $root_dir/$vol)
     for mp in $d ${binds[@]}; do
@@ -532,9 +534,9 @@ umount-then-mount-latest() {
   umount-kill ${to_umount[@]}
   for vol in ${umount_vols[@]}; do
     set-d-binds
+    root_dir=${root_dirs[$vol]}
     if $umount_ret; then
       fresh_snap=$(cat /nocow/btrfs-stale/$vol 2>/dev/null)
-      get-btrfs-root-mountpoint
       mv-vol-to-leaf
       expire-leaf-vols
       b btrfs sub snapshot $fresh_snap $vol
@@ -581,6 +583,8 @@ fi
 ret=0
 mkdir -p /var/log/btrbk
 
+declare -A root_dirs
+
 setup-fstab
 prune-vols
 w mount-mismatch-fix ||: