On Fri, Sep 8, 2023 at 1:37 AM Liu Shixin <liushixin2@xxxxxxxxxx> wrote: > > The variable sc is NULL pointer in can_reclaim_anon_pages() when called > from zone_reclaimable_pages(). Check it before setting swapcache_only. > > Reported-by: Sachin Sant <sachinp@xxxxxxxxxxxxx> > Link: https://lore.kernel.org/linux-mm/F00144DE-2A3F-4463-8203-45E0D57E313E@xxxxxxxxxxxxx/T/ > Fixes: 92039ae85e8d("mm: vmscan: try to reclaim swapcache pages if no swap space") > Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx> > --- > mm/vmscan.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f1dc0dbf1cdb..5eb85ddf403f 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -617,7 +617,7 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, > if (get_nr_swap_pages() > 0) > return true; > /* Is there any swapcache pages to reclaim? */ > - if (total_swapcache_pages() > 0) { > + if (sc && total_swapcache_pages() > 0) { If sc is NULL, we will not return true even if we have pages in the swapcache. This will make can_reclaim_anon_pages() return differently based on whether sc is passed in. Is this the needed behavior? I thought the sc NULL check should be used only to guard the setting of sc->swapcache_only, not the return value as well? > sc->swapcache_only = 1; > return true; > } > @@ -626,7 +626,7 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, > if (mem_cgroup_get_nr_swap_pages(memcg) > 0) > return true; > /* Is there any swapcache pages in memcg to reclaim? */ > - if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) { > + if (sc && mem_cgroup_get_nr_swapcache_pages(memcg) > 0) { > sc->swapcache_only = 1; > return true; > } > -- > 2.25.1 >
