Repair mode for raid6

In repair mode, raid6check will rewrite one single stripe
by regenerating the data (or parity) of two raid devices that
are specified via the command line.
If you need to rewrite just one slot, pick any other slot
at random.

Note that the repair option will change data on the disks
directly, so both the md layer above as well as any layers
above md (such as filesystems) may be accessing the stripe
data from cached buffers. Either instruct the kernels
to drop the caches or reassemble the raid after repair.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/19raid6repair b/tests/19raid6repair
new file mode 100644
index 00000000..4a3e60ca
--- /dev/null
+++ b/tests/19raid6repair
@@ -0,0 +1,47 @@
+number_of_disks=4
+chunksize_in_kib=512
+chunksize_in_b=$[chunksize_in_kib*1024]
+array_data_size_in_kib=$[chunksize_in_kib*(number_of_disks-2)*number_of_disks]
+array_data_size_in_b=$[array_data_size_in_kib*1024]
+devs="$dev1 $dev2 $dev3 $dev4"
+
+# default 32 sectors
+data_offset_in_kib=$[32/2]
+
+for failure in "$dev3 3 3 2" "$dev3 3 2 3" "$dev3 3 2 1" "$dev3 3 2 0" "$dev4 3 3 0" "$dev4 3 3 1" "$dev4 3 3 2" \
+		"$dev1 3 0 1" "$dev1 3 0 2" "$dev1 3 0 3" "$dev2 3 1 0" "$dev2 3 1 2" "$dev2 3 1 3" ; do
+	failure_split=( $failure )
+	device_with_error=${failure_split[0]}
+	stripe_with_error=${failure_split[1]}
+	repair_params="$stripe_with_error ${failure_split[2]} ${failure_split[3]}"
+	start_of_errors_in_kib=$[data_offset_in_kib+chunksize_in_kib*stripe_with_error]
+
+	# make a raid5 from a file
+	dd if=/dev/urandom of=/tmp/RandFile bs=1024 count=$array_data_size_in_kib
+	mdadm -CR $md0 -l6 -n$number_of_disks -c $chunksize_in_kib $devs
+	dd if=/tmp/RandFile of=$md0 bs=1024 count=$array_data_size_in_kib
+	blockdev --flushbufs $md0; sync
+
+	check wait
+	blockdev --flushbufs $devs; sync
+	echo 3 > /proc/sys/vm/drop_caches
+	cmp -s -n $array_data_size_in_b $md0 /tmp/RandFile || { echo sanity cmp failed ; exit 2; }
+
+	dd if=/dev/urandom of=$device_with_error bs=1024 count=$chunksize_in_kib seek=$start_of_errors_in_kib
+	blockdev --flushbufs $device_with_error; sync
+	echo 3 > /proc/sys/vm/drop_caches
+
+	$dir/raid6check $md0 0 0 2>&1 | grep -qs "Error" || { echo should detect errors; exit 2; }
+
+	$dir/raid6check $md0 repair $repair_params > /dev/null || { echo repair failed; exit 2; }
+	blockdev --flushbufs $md0 $devs; sync
+	echo 3 > /proc/sys/vm/drop_caches
+
+	$dir/raid6check $md0 0 0 2>&1 | grep -qs "Error" && { echo errors detected; exit 2; }
+	cmp -s -n $array_data_size_in_b $md0 /tmp/RandFile || { echo cmp failed ; exit 2; }
+
+	mdadm -S $md0
+	udevadm settle
+	blockdev --flushbufs $md0 $devs; sync
+	echo 3 > /proc/sys/vm/drop_caches
+done