Some of the blktests users run tests using kernels with built-in modules to run tests easier and quicker. For that reason, it is desirable to run tests with the built-in scsi_debug [1]. However, some of the scsi_debug parameters can be modified only at module load, as module parameters. They are visible as sysfs attribute files, but they are read-only and not writable. There are ten, read-only scsi_debug parameters used in blktests [2]. Because of these parameters, eight test cases are skipped when scsi_debug is built-in [3]. The values of those parameters are kept as global variables and referred to in many places. Changes in the parameter values affect live scsi_debug hosts and cause various troubles. That is why the parameters are read-only. I once tried to make the parameters non-global and unique to each host, but found this approach will need large code changes in scsi_debug. To minimize the code changes for such parameter changes, I propose to allow the parameter changes "only when scsi_debug has no hosts." Users need to remove all hosts before changing the parameters. With this restriction, users can run tests with any, desired parameter values using the built-in scsi_debug. This series shows how the code will change with this approach. I chose dev_size_mb as the example parameter, which is referred to in multiple blktests test cases. The first patch in the series is preparation. The second patch makes dev_size_mb writable through sysfs only when there is no host. This change will allow the test case block/032 to run with the built-in scsi_debug. Corresponding blktests side changes are available on github [4]. The work for the other listed parameters is in progress. While the work is on going, I would like to ask for comments on this approach. Is this approach acceptable? Is there any other better way? [1] https://lore.kernel.org/linux-block/20220530130811.3006554-1-hch@xxxxxx/ [2] Parameters used in blktests which have read-only sysfs attribute files dev_size_mb sector_size lbpws lbpws10 dix dif zbc zone_cap_mb zone_size_mb zone_nr_conv [3] Test cases skipped with built-in scsi_debug block/009 block/025 block/028 block/032 loop/004 zbd/008 zbd/009 zbd/010 [4] https://github.com/kawasaki/blktests/tree/scsi_debug Shin'ichiro Kawasaki (2): scsi: scsi_debug: Factor out initialization of size parameters scsi: scsi_debug: Allow dev_size_mb changes through sysfs drivers/scsi/scsi_debug.c | 91 ++++++++++++++++++++++++++++++--------- 1 file changed, 70 insertions(+), 21 deletions(-) -- 2.43.0
