Messages in this thread | | | Subject | Re: [Patch v4] mm: thp: remove the defer list related code since this will not happen | From | Yang Shi <> | Date | Fri, 17 Jan 2020 16:57:41 -0800 |
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On 1/17/20 3:38 PM, Wei Yang wrote: > If compound is true, this means it is a PMD mapped THP. Which implies > the page is not linked to any defer list. So the first code chunk will > not be executed. > > Also with this reason, it would not be proper to add this page to a > defer list. So the second code chunk is not correct. > > Based on this, we should remove the defer list related code. > > Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") > > Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> > Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: <stable@vger.kernel.org> [5.4+] > > --- > v4: > * finally we identified the related code is not necessary and not > correct, just remove it > * thanks to Kirill T first spot some problem
Thanks for debugging and figuring this out. Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
> v3: > * remove all review/ack tag since rewrite the changelog > * use deferred_split_huge_page as the example of race > * add cc stable 5.4+ tag as suggested by David Rientjes > > v2: > * move check on compound outside suggested by Alexander > * an example of the race condition, suggested by Michal > --- > mm/memcontrol.c | 18 ------------------ > 1 file changed, 18 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 6c83cf4ed970..27c231bf4565 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5340,14 +5340,6 @@ static int mem_cgroup_move_account(struct page *page, > __mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages); > } > > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (compound && !list_empty(page_deferred_list(page))) { > - spin_lock(&from->deferred_split_queue.split_queue_lock); > - list_del_init(page_deferred_list(page)); > - from->deferred_split_queue.split_queue_len--; > - spin_unlock(&from->deferred_split_queue.split_queue_lock); > - } > -#endif > /* > * It is safe to change page->mem_cgroup here because the page > * is referenced, charged, and isolated - we can't race with > @@ -5357,16 +5349,6 @@ static int mem_cgroup_move_account(struct page *page, > /* caller should have done css_get */ > page->mem_cgroup = to; > > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (compound && list_empty(page_deferred_list(page))) { > - spin_lock(&to->deferred_split_queue.split_queue_lock); > - list_add_tail(page_deferred_list(page), > - &to->deferred_split_queue.split_queue); > - to->deferred_split_queue.split_queue_len++; > - spin_unlock(&to->deferred_split_queue.split_queue_lock); > - } > -#endif > - > spin_unlock_irqrestore(&from->move_lock, flags); > > ret = 0;
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