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>> + unsigned long index; >> + int rc; >> + >> + /* >> + * This is very ugly, it is done instead of adding a lock around >> + * pages->source_mm, which is a performance path for mdev, we just >> + * obtain the write side of all the iova_rwsems which also protects the >> + * pages->source_*. Due to copies we can't know which IOAS could read >> + * from the pages, so we just lock everything. This is the only place >> + * locks are nested and they are uniformly taken in ID order. >> + * >> + * ioas_creation_lock prevents new IOAS from being installed in the >> + * xarray while we do this, and also prevents more than one thread from >> + * holding nested locks. >> + */ >> + down_write(&ictx->ioas_creation_lock); >> + xa_lock(&ictx->objects); >> + lockdep_off(); > > IIRC we used the nested annotation on the down_write instead of the > global lockdep_off? See how mm_take_all_locks() did a similar madness The code you sent me used lockdep_off but had a comment wishing for a better method. I'll try the mm_take_all_locks method. (BTW, sorry for the lag time, I just returned from vacation). - Steve