# check data integrity with raid5 write back cache

# create a 4kB random file and 4 files each with a 1kB chunk of the random file:
#    randfile: ABCD   randchunk[0-3]:  A  B  C  D
#
# then create another random 1kB chunk E, and a new random page with A, B, E, D:
#    randchunk4: E    newrandfile:   ABED
create_random_data() {
    dd if=/dev/urandom of=/tmp/randfile bs=4k count=1
    for x in {0..3}
    do
        dd if=/tmp/randfile of=/tmp/randchunk$x bs=1k count=1 skip=$x count=1
    done

    dd if=/dev/urandom of=/tmp/randchunk4 bs=1k count=1

    rm /tmp/newrandfile
    for x in 0 1 4 3
    do
        cat /tmp/randchunk$x >> /tmp/newrandfile
    done
}

# create array, $1 could be 5 for raid5 and 6 for raid6
create_array() {
    if [ $1 -lt 5 -o $1 -gt 6 ]
    then
        echo wrong array type $1
        exit 2
    fi

    mdadm -CR $md0 -c4 -l5 -n10 $dev0 $dev1 $dev2 $dev3 $dev4 $dev5 $dev6 $dev11 $dev8 $dev9 --write-journal $dev10
    check wait
    echo write-back > /sys/block/md0/md/journal_mode
}

restart_array_write_back() {
    mdadm -S $md0
    mdadm -A $md0 $dev0 $dev1 $dev2 $dev3 $dev4 $dev5 $dev6 $dev11 $dev8 $dev9 $dev10
    echo write-back > /sys/block/md0/md/journal_mode
}

# compare the first page of md0 with file in $1
cmp_first_page() {
    cmp  -n 4096 $1 $md0 || { echo cmp failed ; exit 2 ; }
}

# write 3 pages after the first page of md0
write_three_pages() {
    for x in {1..3}
    do
        dd if=/dev/urandom of=$md0 bs=4k count=1 seek=$x count=1
    done
}

# run_test <array_type:5/6> <degraded_or_not:yes/no>
run_test() {
    create_random_data
    create_array $1

    if [ $2 == yes ]
    then
        mdadm --fail $md0 $dev0
    fi

    dd if=/tmp/randfile of=$md0 bs=4k count=1
    restart_array_write_back
    cmp_first_page /tmp/randfile
    restart_array_write_back
    write_three_pages
    cmp_first_page /tmp/randfile


    dd if=/tmp/randchunk4 of=/dev/md0 bs=1k count=1 seek=2
    restart_array_write_back
    cmp_first_page /tmp/newrandfile
    restart_array_write_back
    write_three_pages
    cmp_first_page /tmp/newrandfile

    mdadm -S $md0
}

run_test 5 no
run_test 5 yes
run_test 6 no
run_test 6 yes