The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

ac86f547ca10 ("mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath()") 203a31516616 ("mm/writeback: Add __folio_mark_dirty()") 9d8053fc7a21 ("mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath() to folio") a49d0c507759 ("mm/writeback: Add folio_wait_stable()") 490e016f229a ("mm/writeback: Add folio_wait_writeback()") 4268b48077e5 ("mm/filemap: Add folio_end_writeback()") 575ced1c8b0d ("mm/swap: Add folio_rotate_reclaimable()") 4e1364286d0a ("mm/filemap: Add folio_unlock()") 2f52578f9c64 ("mm/util: Add folio_mapping() and folio_file_mapping()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ac86f547ca1002aec2ef66b9e64d03f45bbbfbb9 Mon Sep 17 00:00:00 2001 From: Kefeng Wang wangkefeng.wang@huawei.com Date: Sun, 29 Jan 2023 12:09:45 +0800 Subject: [PATCH] mm: memcg: fix NULL pointer in mem_cgroup_track_foreign_dirty_slowpath()

As commit 18365225f044 ("hwpoison, memcg: forcibly uncharge LRU pages"), hwpoison will forcibly uncharg a LRU hwpoisoned page, the folio_memcg could be NULl, then, mem_cgroup_track_foreign_dirty_slowpath() could occurs a NULL pointer dereference, let's do not record the foreign writebacks for folio memcg is null in mem_cgroup_track_foreign_dirty() to fix it.

Link: https://lkml.kernel.org/r/20230129040945.180629-1-wangkefeng.wang@huawei.com Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Reported-by: Ma Wupeng mawupeng1@huawei.com Tested-by: Miko Larsson mikoxyzzz@gmail.com Acked-by: Michal Hocko mhocko@suse.com Cc: Jan Kara jack@suse.cz Cc: Jens Axboe axboe@kernel.dk Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Ma Wupeng mawupeng1@huawei.com Cc: Naoya Horiguchi naoya.horiguchi@nec.com Cc: Shakeel Butt shakeelb@google.com Cc: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index d3c8203cab6c..85dc9b88ea37 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1666,10 +1666,13 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct folio *folio, static inline void mem_cgroup_track_foreign_dirty(struct folio *folio, struct bdi_writeback *wb) { + struct mem_cgroup *memcg; + if (mem_cgroup_disabled()) return;

- if (unlikely(&folio_memcg(folio)->css != wb->memcg_css)) + memcg = folio_memcg(folio); + if (unlikely(memcg && &memcg->css != wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(folio, wb); }