If there are no objection to the patch I will post it as a standalong one. On Mon 26-08-19 12:55:21, Michal Hocko wrote: > From 59d128214a62bf2d83c2a2a9cde887b4817275e7 Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@xxxxxxxx> > Date: Mon, 26 Aug 2019 12:43:15 +0200 > Subject: [PATCH] mm, memcg: do not set reclaim_state on soft limit reclaim > > Adric Blake has noticed the following warning: > [38491.963105] WARNING: CPU: 7 PID: 175 at mm/vmscan.c:245 set_task_reclaim_state+0x1e/0x40 > [...] > [38491.963239] Call Trace: > [38491.963246] mem_cgroup_shrink_node+0x9b/0x1d0 > [38491.963250] mem_cgroup_soft_limit_reclaim+0x10c/0x3a0 > [38491.963254] balance_pgdat+0x276/0x540 > [38491.963258] kswapd+0x200/0x3f0 > [38491.963261] ? wait_woken+0x80/0x80 > [38491.963265] kthread+0xfd/0x130 > [38491.963267] ? balance_pgdat+0x540/0x540 > [38491.963269] ? kthread_park+0x80/0x80 > [38491.963273] ret_from_fork+0x35/0x40 > [38491.963276] ---[ end trace 727343df67b2398a ]--- > > which tells us that soft limit reclaim is about to overwrite the > reclaim_state configured up in the call chain (kswapd in this case but > the direct reclaim is equally possible). This means that reclaim stats > would get misleading once the soft reclaim returns and another reclaim > is done. > > Fix the warning by dropping set_task_reclaim_state from the soft reclaim > which is always called with reclaim_state set up. > > Reported-by: Adric Blake <promarbler14@xxxxxxxxx> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/vmscan.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c77d1e3761a7..a6c5d0b28321 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3220,6 +3220,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > > #ifdef CONFIG_MEMCG > > +/* Only used by soft limit reclaim. Do not reuse for anything else. */ > unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, > gfp_t gfp_mask, bool noswap, > pg_data_t *pgdat, > @@ -3235,7 +3236,8 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, > }; > unsigned long lru_pages; > > - set_task_reclaim_state(current, &sc.reclaim_state); > + WARN_ON_ONCE(!current->reclaim_state); > + > sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | > (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); > > @@ -3253,7 +3255,6 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, > > trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); > > - set_task_reclaim_state(current, NULL); > *nr_scanned = sc.nr_scanned; > > return sc.nr_reclaimed; > -- > 2.20.1 > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs
