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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id y19sm278969edu.90.2019.08.28.00.18.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Aug 2019 00:18:39 -0700 (PDT) From: Michal Hocko To: Andrew Morton , Johannes Weiner Cc: Hillf Danton , , LKML , Michal Hocko , Adric Blake , Yafang Shao , Yang Shi Subject: [PATCH] mm, memcg: do not set reclaim_state on soft limit reclaim Date: Wed, 28 Aug 2019 09:18:08 +0200 Message-Id: <20190828071808.20410-1-mhocko@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko Adric Blake has noticed[1] 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 Acked-by: Yafang Shao Acked-by: Yang Shi Signed-off-by: Michal Hocko [1] http://lkml.kernel.org/r/CAE1jjeePxYPvw1mw2B3v803xHVR_BNnz0hQUY_JDMN8ny29M6w@mail.gmail.com --- 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