From 3d4d75c519c435337a04eec4cc16ab0296f2c507 Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Thu, 15 Apr 2021 02:51:11 +0100
Subject: [PATCH] uvol: make volume creation atomic

Make sure filesystem is ready when volume becomes available.
Use 'write-once' as initial state for read-only volumes, only allow
writing to volumes in that state and transision to 'read-only' once
write has completed.
Also fix a typo which prevented 'list' command from working with LVM.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 utils/uvol/files/lvm.sh | 39 +++++++++++++++++++++++++++------------
 utils/uvol/files/ubi.sh | 40 +++++++++++++++++++++-------------------
 utils/uvol/files/uvol   |  2 --
 3 files changed, 48 insertions(+), 33 deletions(-)

diff --git a/utils/uvol/files/lvm.sh b/utils/uvol/files/lvm.sh
index 35c2ae17e4..158ab1c83d 100644
--- a/utils/uvol/files/lvm.sh
+++ b/utils/uvol/files/lvm.sh
@@ -41,7 +41,7 @@ vgs() {
 }
 
 lvs() {
-	lvm_cmd vgs --reportformat json --units b "$@"
+	lvm_cmd lvs --reportformat json --units b "$@"
 }
 
 freebytes() {
@@ -121,7 +121,7 @@ exportlv() {
 	lv_size=
 	json_init
 
-	json_load "$(lvs -o lv_full_name,lv_size,lv_path,lv_dm_path -S "lv_name=~^r[ow]_$1\$ && vg_name=$vg_name")"
+	json_load "$(lvs -o lv_full_name,lv_size,lv_path,lv_dm_path -S "lv_name=~^[rw][ow]_$1\$ && vg_name=$vg_name")"
 	json_select report
 	json_get_keys reports
 	for rep in $reports; do
@@ -153,7 +153,15 @@ getsize() {
 
 activatevol() {
 	exportlv "$1"
-	lvm_cmd lvchange -a y "$lv_full_name"
+	case "$lv_path" in
+		/dev/*/wo_*)
+			return 22
+			;;
+		*)
+			lvm_cmd lvchange -a y "$lv_full_name"
+			return 0
+			;;
+	esac
 }
 
 disactivatevol() {
@@ -169,7 +177,7 @@ getstatus() {
 }
 
 createvol() {
-	local mode ret
+	local mode lvmode ret
 	local volsize=$(($2))
 	[ "$volsize" ] || return 22
 	exportlv "$1"
@@ -178,10 +186,12 @@ createvol() {
 	[ $((size_ext * vg_extent_size)) -lt $volsize ] && size_ext=$((size_ext + 1))
 
 	case "$3" in
-		ro)
-			mode=r
+		ro|wo)
+			lvmode=r
+			mode=wo
 			;;
 		rw)
+			lvmode=rw
 			mode=rw
 			;;
 		*)
@@ -189,9 +199,9 @@ createvol() {
 			;;
 	esac
 
-	lvm_cmd lvcreate -p $mode -a n -y -W n -Z n -n "${3}_${1}" -l "$size_ext" $vg_name
+	lvm_cmd lvcreate -p $lvmode -a n -y -W n -Z n -n "${mode}_${1}" -l "$size_ext" $vg_name
 	ret=$?
-	if [ ! $ret -eq 0 ] || [ "$mode" = "r" ]; then
+	if [ ! $ret -eq 0 ] || [ "$lvmode" = "r" ]; then
 		return $ret
 	fi
 	exportlv "$1"
@@ -215,11 +225,16 @@ updatevol() {
 	exportlv "$1"
 	[ "$lv_full_name" ] || return 2
 	[ $lv_size -ge $2 ] || return 27
-	lvm_cmd lvchange -a y -p rw "$lv_full_name"
-	dd of=$lv_path
 	case "$lv_path" in
-		/dev/*/ro_*)
+		/dev/*/wo_*)
+			lvm_cmd lvchange -a y -p rw "$lv_full_name"
+			dd of=$lv_path
 			lvm_cmd lvchange -p r "$lv_full_name"
+			lvm_cmd lvrename "$lv_full_name" "${lv_full_name%%/*}/ro_$1"
+			return 0
+			;;
+		default)
+			return 22
 			;;
 	esac
 }
@@ -228,7 +243,7 @@ listvols() {
 	local reports rep lv lvs lv_name lv_size lv_mode volname
 	volname=${1:-.*}
 	json_init
-	json_load "$(lvs -o lv_name,lv_size -S "lv_name=~^r[ow]_$volname\$ && vg_name=$vg_name")"
+	json_load "$(lvs -o lv_name,lv_size -S "lv_name=~^[rw][ow]_$volname\$ && vg_name=$vg_name")"
 	json_select report
 	json_get_keys reports
 	for rep in $reports; do
diff --git a/utils/uvol/files/ubi.sh b/utils/uvol/files/ubi.sh
index 28841ca047..7851a98df4 100644
--- a/utils/uvol/files/ubi.sh
+++ b/utils/uvol/files/ubi.sh
@@ -31,17 +31,17 @@ getdev() {
 	local voldir volname devname
 	for voldir in /sys/devices/virtual/ubi/${ubidev}/${ubidev}_*; do
 		read volname < "${voldir}/name"
-		[ "$volname" = "uvol-ro-$1" ] || [ "$volname" = "uvol-rw-$1" ] || continue
+		[ "$volname" = "uvol-ro-$1" ] || [ "$volname" = "uvol-wp-$1" ] || [ "$volname" = "uvol-rw-$1" ] || [ "$volname" = "uvol-wo-$1" ] || continue
 		basename "$voldir"
 	done
 }
 
-needs_ubiblock() {
+vol_is_mode() {
 	local voldev="$1"
 	local volname
 	read volname < "/sys/devices/virtual/ubi/${ubidev}/${voldev}/name"
 	case "$volname" in
-		uvol-ro-*)
+		uvol-$2-*)
 			return 0
 			;;
 	esac
@@ -51,7 +51,8 @@ needs_ubiblock() {
 getstatus() {
 	local voldev=$(getdev "$@")
 	[ "$voldev" ] || return 2
-	needs_ubiblock $voldev && [ ! -e "/dev/ubiblock${voldev:3}" ] && return 1
+	vol_is_mode $voldev wo && return 1
+	vol_is_mode $voldev ro && [ ! -e "/dev/ubiblock${voldev:3}" ] && return 1
 	return 0
 }
 
@@ -65,9 +66,9 @@ getsize() {
 getuserdev() {
 	local voldev=$(getdev "$@")
 	[ "$voldev" ] || return 2
-	if needs_ubiblock $voldev ; then
+	if vol_is_mode $voldev ro ; then
 		echo "/dev/ubiblock${voldev:3}"
-	else
+	elif vol_is_mode $voldev rw ; then
 		echo "/dev/$voldev"
 	fi
 }
@@ -77,11 +78,11 @@ createvol() {
 	local existdev=$(getdev "$@")
 	[ "$existdev" ] && return 17
 	case "$3" in
-		ro)
-			mode=ro
+		ro|wo)
+			mode=wo
 			;;
 		rw)
-			mode=rw
+			mode=wp
 			;;
 		*)
 			return 22
@@ -91,6 +92,12 @@ createvol() {
 	ret=$?
 	[ $ret -eq 0 ] || return $ret
 	ubiupdatevol -t /dev/$(getdev "$@")
+	[ "$mode" = "wp" ] || return 0
+	local tmp_mp=$(mktemp -d)
+	mount -t ubifs /dev/$(getdev "$@") $tmp_mp
+	umount $tmp_mp
+	rmdir $tmp_mp
+	ubirename /dev/$ubidev uvol-wp-$1 uvol-rw-$1
 }
 
 removevol() {
@@ -103,7 +110,8 @@ removevol() {
 activatevol() {
 	local voldev=$(getdev "$@")
 	[ "$voldev" ] || return 2
-	needs_ubiblock $voldev || return 0
+	vol_is_mode $voldev wo || return 1
+	vol_is_mode $voldev ro || return 0
 	[ -e "/dev/ubiblock${voldev:3}" ] && return 0
 	ubiblock --create /dev/$voldev
 }
@@ -111,7 +119,7 @@ activatevol() {
 disactivatevol() {
 	local voldev=$(getdev "$@")
 	[ "$voldev" ] || return 2
-	needs_ubiblock $voldev || return 0
+	vol_is_mode $voldev ro || return 0
 	[ -e "/dev/ubiblock${voldev:3}" ] || return 0
 	ubiblock --remove /dev/$voldev
 }
@@ -120,15 +128,9 @@ updatevol() {
 	local voldev=$(getdev "$@")
 	[ "$voldev" ] || return 2
 	[ "$2" ] || return 22
-	needs_ubiblock $voldev || return 22
+	vol_is_mode $voldev wo || return 22
 	ubiupdatevol -s $2 /dev/$voldev -
-}
-
-getstatus() {
-	local voldev=$(getdev "$@")
-	[ "$voldev" ] || return 2
-	needs_ubiblock $voldev && [ ! -e "/dev/ubiblock${voldev:3}" ] && return 1
-	return 0
+	ubirename /dev/$ubidev uvol-wo-$1 uvol-ro-$1
 }
 
 listvols() {
diff --git a/utils/uvol/files/uvol b/utils/uvol/files/uvol
index 58d08f07e1..0fea88f38c 100644
--- a/utils/uvol/files/uvol
+++ b/utils/uvol/files/uvol
@@ -2,8 +2,6 @@
 
 # uvol prototype
 # future development roadmap (aka. to-do):
-# * atomic create using temp volnames
-# * create read-only volumes as 'write-once', introduce 'pending' state until written
 # * re-implement in C (use libubox, execve lvm/ubi*)
 # * add atomic batch processing for use by container/package manager