Bug#417407: Improve safety of os-prober by ignoring active swap and using "blockdev --setro" when available

["Alex Owen" <r.alex.owen@gmail.com>]

OK here is the patch!

On 07/04/07, Alex Owen <r.alex.owen@gmail.com> wrote:
> Attached is a patch to os-prober to:
> (1) make it ignore active swap
> [Changes in: os-prober/os-prober]
>
> (2) if blockdev is available then use it to set partitions read-only
> before mounting to work arround a "feature" of ext3 and possible other
> journaled filesystems!
> [Changes in: os-prober/os-probes/common/50mounted-tests]
Index: os-prober/os-prober
===================================================================
--- os-prober/os-prober	(revision 46179)
+++ os-prober/os-prober	(working copy)
@@ -34,6 +34,13 @@
 	done
 }
 
+parse_proc_swaps () {
+	while read line; do
+		set -- $line
+		echo "$(mapdevfs $1) swap swap"
+	done
+}
+
 parse_proc_mdstat () {
 	while read line; do
 		for word in $line; do
@@ -67,6 +74,7 @@
 # Therefore we use mapdevfs to match partitions with mount points
 # and partitions used in RAID
 grep "^/dev/" /proc/mounts | parse_proc_mounts >/tmp/mounted-map || true
+grep "^/dev/" /proc/swaps | parse_proc_swaps >/tmp/swaps-map || true
 : >/tmp/raided-map
 if [ -f /proc/mdstat ] ; then
 	grep "^md" /proc/mdstat | parse_proc_mdstat >/tmp/raided-map || true
@@ -84,6 +92,12 @@
 		continue
 	fi
 
+	# Skip partitions used as active swap
+	if grep -q "^$mapped" /tmp/swaps-map ; then
+		debug "$partition: is active swap"
+		continue
+	fi
+
 	if ! grep -q "^$mapped " /tmp/mounted-map ; then
 		for test in /usr/lib/os-probes/*; do
 			if [ -f $test ] && [ -x $test ]; then
Index: os-prober/os-probes/common/50mounted-tests
===================================================================
--- os-prober/os-probes/common/50mounted-tests	(revision 46179)
+++ os-prober/os-probes/common/50mounted-tests	(working copy)
@@ -20,6 +20,25 @@
 	fi
 done
 
+
+protect_dev(){ #$1=partition : stdout=dev_rw_flag
+dev_rw_flag=0
+if type blockdev >/dev/null 2>&1; then
+	if  [ `blockdev --getro $1` = "0" ] ; then 
+		blockdev --setro $1
+		dev_rw_flag=1
+	fi
+fi
+echo $dev_rw_flag
+}
+
+unprotect_dev(){ #$1=partition $2=dev_rw_flag
+if  [ "$2" = "1" ] ; then 
+	blockdev --setrw $1
+fi
+}
+
+dev_rw_flag=`protect_dev $partition`
 for type in $types $delaytypes; do
 	if mount -o ro -t $type $partition $tmpmnt 2>/dev/null; then
 		debug "mounted as $type filesystem"
@@ -29,6 +48,7 @@
 				if $test $partition $tmpmnt $type; then
 					debug "os found by subtest $test"
 					umount $tmpmnt
+					unprotect_dev $partition $dev_rw_flag
 					rmdir $tmpmnt || true
 					exit 0
 				fi
@@ -38,6 +58,7 @@
 		break
 	fi
 done
+unprotect_dev $partition $dev_rw_flag
 
 rmdir $tmpmnt || true