Li Zefan wrote: > Balbir Singh wrote: >> YAMAMOTO Takashi wrote: >>>> Li Zefan wrote: >>>>> No need for VM_BUG_ON(pc), since 'pc' is the list entry. This should >>>>> be VM_BUG_ON(page). >>>>> >>>>> Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx> >>>>> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> >>>> pc is of type page_cgroup and we use list_for_each_entry_safe_reverse. Not sure >>>> why we can't bug on pc. >>> pc is dereferenced before this VM_BUG_ON. >>> >>> YAMAMOTO Takashi >>> >> OK, so the VM_BUG_ON needs to move to an earlier location. Agreed. >> > > No, 'pc' has been dereferenced in list_for_each_entry_safe_reverse(). > > > #define list_for_each_entry_safe_reverse(pos, n, head, member) \ > for (pos = list_entry((head)->prev, typeof(*pos), member), \ > n = list_entry(pos->member.prev, typeof(*pos), member); \ > ^^^^^^^^^^^ > &pos->member != (head); \ > ^^^^^^^^^^^ > pos = n, n = list_entry(n->member.prev, typeof(*n), member)) > Hmm.. We used to have a for loop with !list_empty() as a termination condition and VM_BUG_ON(!pc) is a spill over. With the new loop, VM_BUG_ON(!pc) does not make sense. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
