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Unfortunatelly on kernels <4.16 lvm2 can't user brd ramdisks
for backend device as number of test is failing with this kernel
message:
device-mapper: ioctl: can't change device type after initial table load.
caused by DAX request-based handling, and lvm2 tries to replace device
with backend 'error' bio-based device and such table reload is being
rejected.
So ATM keep ramdisk only on most recent kernel to experiment a bit,
for older machines just stay safe and keep old slower loop backend.
Just like 52656c89fd
when now cache is compiled in 'unditionally'.
This patch is actually enforce by changes in
commit: 2bc896f2a3
where CACHE value is not set anymore.
If the test does not need root, it can use 'SKIP_ROOT_DM_CHECK'.
For such test no actions needed root to initilize DM devices and
nodes will be take and test can check i.e. functional unit tests.
Usage of dm_delay looks to be slowing not just 'delayed' portion
of device, but due to the fact it's also slows down ANY flush
operation on such device it's overal speed impact is huge.
In some case we can however user other methods to slowdown disk writes,
in case of old dm 'mirror' target we can throttle I/O of mirror
synchronisation giving the next commands enough time to test couple
race conditions.
Usage:
throttle_dm_mirror [percentage]
Thtrottle down sync speed (lowest is '1' which is also default when
unspecified)
restore_dm_mirror
Restores the value of throttling before call of 'throttle_dm_mirror'
Usually it should '100'
Currently usage of loop device over backend file in ramdisk (tmpfs)
is actually causing unnecassary memory consution, since just
reading such loop device is causing RAM provisioning.
This patch add another possible way how to use ramdisk directly
through 'brd' device when possible (and allowed).
This however has it's limitation as well - brd does not support
TRIM, so the only way how to erase is to remove brd module ??
Alse there is 4K sector size limitation imposed by ramdisk.
Anyway - for some mirror test that were using large amount of
disk space (tens of MB) this brings noticable speed boost.
(But could be worth to solve the slowness of loop in kernel?)
To prevent using 'brd' for testing set LVM_TEST_PREFER_BRD=0
like this:
make check_local LVM_TEST_PREFER_BRD=0
When 'dmsetup' reports result with --nameprefixes it currently
incorrectly 'escapes' problematic characters.
Letting pass such string though shell 'eval' function is hard task.
So instead cut away substring.
Once dmsetup will start to properly escape backslash and apostrophe
this function may need further tuning.
With problematic kernels raid devices can be occasionaly left with
'frozen' status - try to 'unfreeze' them with idle message on teardown.
Also replace couple greps with 'built-in' dmsetup --select feature.
Note: dmsetup --select currently reports 'No devices found' on stdout
and return success - looks like a bug to fix.
This is somewhat tricky - for test suite we keep using
'set -e -o pipefail' - the effect here is - we get error report
from any 'failing' command in whole pipeline - thus when something
like this: 'lvs | head -1' is used - and 'head' finishes before
lead 'lvs' is done - it recieves SIGPIPE and exits with error,
and somewhat misleading gets occasionally reported depending
of speed of commands.
For this case we have to avoid using standard pipes and rather
switch to using streamed results with temporary output file.
This is all nicely handled with bash feature '< <()'.
For more info:
https://stackoverflow.com/questions/41516177/bash-zcat-head-causes-pipefail
Sleep a bit before checking /sys/block dir so the kernel has a moment to
actually put scsi debug device in it...
Some quite old kernels are in troubles with this plain searching grep
without sleep (namely 2.6.32)
modprobe scsi_debug
<sleep .1>
grep -H scsi_debug /sys/block/*/device/model
modprobe -r scsi_debug
lvmdbusd was started, but the process was not recognized by pgrep.
- configure does not make the script executable - set the flag
explicitly when running make check,
- process name changed to lvmdbusd. The previous python3 value
originated from the use of /usr/bin/env.
Just like with other vars support this:
make check_local T=xyz LVM_LOG_FILE_MAX_LINES=10000000
Allows easily to override existing line limit.
Also increase limiting size of logs per command since some of
our commands are becoming very verbose....
Avoid starting test, when test dir has less then 50M of free space.
Better to crash early before letting die machine on weird crash
in OOM cases...
Also show free disk space when test starts
Commit 8a912d6dbc missed the wrong logic,
we use 2 vars 'dev' & 'mddev' and their usage can't be mixed.
So correctly separate them so mddev keeps name of MD device.
