Re: [PATCH] wic-img: Fix bind mounting

[Jan Kiszka <jan.kiszka@siemens.com>]

On 06.12.18 10:44, Maxim Yu. Osipov wrote:
> Just to doublecheck: What is your patch queue for that?
> 

Just updated jan/queue on github.com/siemens/isar. It's not the best ordering of 
patches, this fix should probably come earlier, but the top is what I tested 
successfully also in a stretch VM.

Jan

> On 12/6/18 11:13 AM, Jan Kiszka wrote:
>>
>> This addresses two issues of the current code:
>>
>>   - we must make the bind mount of STAGING_DIR private because it will
>>     otherwise pick up bind mounts done underneath it in the various
>>     rootfs used by parallel targets
>>
>>   - locking was missing to make check and mount atomic, just like we do
>>     inside buildchroot_do_mounts
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>
>> My theory on what went wrong /wrt rbind-mounted /sys and /dev: As the
>> bind-mounting of STAGING_DIR of a wic target (qemu-amd64) eventually
>> started to contain shared(!) bind-mounts of parallel targets (qemu-
>> armhf, qemu-arm64), and all those stick to the end, isar_handler started
>> to umount their now also shared /dev and /sys mounts. And that
>> destroyed the host mounts.
>>
>> Lesson to be recalled: never paper over issues that were not yet fully
>> understood. They may point to sleeping problems that will only bite you
>> again later.
>>
>>   meta/classes/wic-img.bbclass | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/meta/classes/wic-img.bbclass b/meta/classes/wic-img.bbclass
>> index 225463e..76602d8 100644
>> --- a/meta/classes/wic-img.bbclass
>> +++ b/meta/classes/wic-img.bbclass
>> @@ -87,11 +87,14 @@ do_build[stamp-extra-info] = "${DISTRO}-${DISTRO_ARCH}"
>>   do_wic_image() {
>>       buildchroot_do_mounts
>> -    for dir in ${BBLAYERS} ${STAGING_DIR} ${ISARROOT}/scripts; do
>> -    sudo mkdir -p ${BUILDCHROOT_DIR}/$dir
>> -        mountpoint ${BUILDCHROOT_DIR}/$dir >/dev/null 2>&1 \
>> -        || sudo mount --bind $dir ${BUILDCHROOT_DIR}/$dir
>> -    done
>> +    sudo flock ${MOUNT_LOCKFILE} -c ' \
>> +        for dir in ${BBLAYERS} ${STAGING_DIR} ${ISARROOT}/scripts; do
>> +            mkdir -p ${BUILDCHROOT_DIR}/$dir
>> +            if ! mountpoint ${BUILDCHROOT_DIR}/$dir >/dev/null 2>&1; then
>> +                mount --bind --make-private $dir ${BUILDCHROOT_DIR}/$dir
>> +            fi
>> +        done
>> +        '
>>       export FAKEROOTCMD=${FAKEROOTCMD}
>>       export BUILDDIR=${BUILDDIR}
>>       export MTOOLS_SKIP_CHECK=1
>>
> 
> 

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