On (23/04/17 04:16), Yosry Ahmed wrote: > > That's a good question to which I don't have an answer. We can list_add() > > the same zspage twice, unlocking the pool after first list_add() so that > > another process (including another zs_compact()) can do something to that > > zspage. The answer is somewhere between these lines, I guess. > > But the first list_add() is (in this case) the correct add, so we > expect other processes to be able to access the zspage after the first > list_add() anyway, right? Correct. Compaction also can unlock pool->lock and schedule() so that another process can access the source zspage, when compaction gets scheduled it can attempt putback/unlock the same zspage one more time (the zspage may not even exist at this point, I assume).
