On Tue, Jul 2, 2019 at 6:57 PM Henry Burns <henryburns@xxxxxxxxxx> wrote: > > On Tue, Jul 2, 2019 at 12:45 AM Vitaly Wool <vitalywool@xxxxxxxxx> wrote: > > > > Hi Henry, > > > > On Mon, Jul 1, 2019 at 8:31 PM Henry Burns <henryburns@xxxxxxxxxx> wrote: > > > > > > Running z3fold stress testing with address sanitization > > > showed zhdr->slots was being used after it was freed. > > > > > > z3fold_free(z3fold_pool, handle) > > > free_handle(handle) > > > kmem_cache_free(pool->c_handle, zhdr->slots) > > > release_z3fold_page_locked_list(kref) > > > __release_z3fold_page(zhdr, true) > > > zhdr_to_pool(zhdr) > > > slots_to_pool(zhdr->slots) *BOOM* > > > > Thanks for looking into this. I'm not entirely sure I'm all for > > splitting free_handle() but let me think about it. > > > > > Instead we split free_handle into two functions, release_handle() > > > and free_slots(). We use release_handle() in place of free_handle(), > > > and use free_slots() to call kmem_cache_free() after > > > __release_z3fold_page() is done. > > > > A little less intrusive solution would be to move backlink to pool > > from slots back to z3fold_header. Looks like it was a bad idea from > > the start. > > > > Best regards, > > Vitaly > > We still want z3fold pages to be movable though. Wouldn't moving > the backink to the pool from slots to z3fold_header prevent us from > enabling migration? That is a valid point but we can just add back pool pointer to z3fold_header. The thing here is, there's another patch in the pipeline that allows for a better (inter-page) compaction and it will somewhat complicate things, because sometimes slots will have to be released after z3fold page is released (because they will hold a handle to another z3fold page). I would prefer that we just added back pool to z3fold_header and changed zhdr_to_pool to just return zhdr->pool, then had the compaction patch valid again, and then we could come back to size optimization. Best regards, Vitaly
