Re: [PATCH] blktests: replace module removal with patient module removal

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On 11/16/21 9:29 AM, Luis Chamberlain wrote:
> A long time ago, in a galaxy far, far away...
> 
> I ran into some odd scsi_debug false positives with fstests. This
> prompted me to look into them given these false positives prevents
> me from moving forward with establishing a test baseline with high
> number of cycles. That is, this stupid issue was prevening creating
> high confidence in testing.
> 
> I reported it [0] and exchanged some ideas with Doug. However, in
> the end, despite efforts to help things with scsi_debug there were
> still issues lingering which seemed to defy our expectations upstream.
> One of the last hanging fruit issues is and always has been that
> userspace expectations for proper module removal has been broken,
> so in the end I have demonstrated this is a generic issue [1].
> 
> Long ago a WAIT option for module removal was added... that was then
> removed as it was deemed not needed as folks couldn't figure out when
> these races happened. The races are actually pretty easy to trigger, it
> was just never properly documented. A simpe blkdev_open() will easily
> bump a module refcnt, and these days many thing scan do that sort of
> thing.
> 
> The proper solution is to implement then a patient module removal
> on kmod and patches have been sent for that and those patches are
> under review. In the meantime we need a work around to open code a
> similar solution for users of old versions of kmod. I sent an open
> coded solution for fstests about since August 19th and has been used
> there for a few months now. Now that that stuff is merged and tested
> in fstests with more exposure, its time to match parity on blktests.
> 
> I've tested blktests with this for things which I can run virtually
> for a while now. More wider testig is welcomed.
> 
> [0] https://bugzilla.kernel.org/show_bug.cgi?id=212337
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=214015
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---


This looks good to me, I'd wait Bart (CCd here) to review the
srp side.

Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>





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