On 11/16/21 09:29, 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> > Thanks for having this work done and explaining the importance of it. Give me couple of days, I'll provide you a feedback after I finish my testing of your patch.
