On 3/4/20 3:22 AM, Kees Cook wrote: > On Tue, Mar 03, 2020 at 05:26:14PM -0800, David Rientjes wrote: > > Seems reasonable! > > For the race concerns, should this logic just make sure the resulting > order can never shrink? Or does it need much stronger atomicity? If order grows, I think we also need to recalculate the random sequence for freelist randomization [1]. I expect that would be rather problematic with parallel allocations/freeing going on. As was also noted, the any_slab_objects(s) checks are racy - might return false and immediately some other CPU can allocate some. I wonder if this race window could be fixed at all without introducing extra locking in the fast path? Which means it's probably not worth the trouble of having these runtime knobs. How about making the files read-only (if not remove completely). Vijayanand described a use case in [2], shouldn't it be possible to implement that scenario (all caches have debugging enabled except zram cache) with kernel parameters only? Thanks, Vlastimil [1] https://lore.kernel.org/linux-mm/d3acc069-a5c6-f40a-f95c-b546664bc4ee@xxxxxxx/ [2] https://lore.kernel.org/linux-mm/1383cd32-1ddc-4dac-b5f8-9c42282fa81c@xxxxxxxxxxxxxx/
