Michal Hocko <mhocko@xxxxxxx> writes: > On Mon 11-06-12 15:10:20, Aneesh Kumar K.V wrote: >> Michal Hocko <mhocko@xxxxxxx> writes: > [...] >> >> +static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup, >> >> + struct page *page) >> > >> > deserves a comment about the locking (needs to be called with >> > hugetlb_lock). >> >> will do >> >> > >> >> +{ >> >> + int csize; >> >> + struct res_counter *counter; >> >> + struct res_counter *fail_res; >> >> + struct hugetlb_cgroup *page_hcg; >> >> + struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup); >> >> + struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup); >> >> + >> >> + if (!get_page_unless_zero(page)) >> >> + goto out; >> >> + >> >> + page_hcg = hugetlb_cgroup_from_page(page); >> >> + /* >> >> + * We can have pages in active list without any cgroup >> >> + * ie, hugepage with less than 3 pages. We can safely >> >> + * ignore those pages. >> >> + */ >> >> + if (!page_hcg || page_hcg != h_cg) >> >> + goto err_out; >> > >> > How can we have page_hcg != NULL && page_hcg != h_cg? >> >> pages belonging to other cgroup ? > > OK, I've forgot that you are iterating over all active huge pages in > hugetlb_cgroup_pre_destroy. What prevents you from doing the filtering > in the caller? > I am also wondering why you need to play with the page reference > counting here. You are under hugetlb_lock so the page cannot disappear > in the meantime or am I missing something? That is correct. Updated the patch and also added the below comment to the function. + +/* + * Should be called with hugetlb_lock held. + * Since we are holding hugetlb_lock, pages cannot get moved from + * active list or uncharged from the cgroup, So no need to get + * page reference and test for page active here. + */ -aneesh -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html