mm/cgroup/reclaim: fix dirty pages throttling on cgroup v1

balance_dirty_pages doesn't do the required dirty throttling on cgroupv1.
See commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writeback
on traditional hierarchies").  Instead, the kernel depends on writeback
throttling in shrink_folio_list to achieve the same goal.  With large
memory systems, the flusher may not be able to writeback quickly enough
such that we will start finding pages in the shrink_folio_list already in
writeback.  Hence for cgroupv1 let's do a reclaim throttle after waking up
the flusher.

The below test which used to fail on a 256GB system completes till the the
file system is full with this change.

root@lp2:/sys/fs/cgroup/memory# mkdir test
root@lp2:/sys/fs/cgroup/memory# cd test/
root@lp2:/sys/fs/cgroup/memory/test# echo 120M > memory.limit_in_bytes
root@lp2:/sys/fs/cgroup/memory/test# echo $$ > tasks
root@lp2:/sys/fs/cgroup/memory/test# dd if=/dev/zero of=/home/kvaneesh/test bs=1M
Killed

Link: https://lkml.kernel.org/r/20221118070603.84081-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: zefan li <lizefan.x@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e366666..026199c 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2514,8 +2514,20 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
         * the flushers simply cannot keep up with the allocation
         * rate. Nudge the flusher threads in case they are asleep.
         */
-       if (stat.nr_unqueued_dirty == nr_taken)
+       if (stat.nr_unqueued_dirty == nr_taken) {
                wakeup_flusher_threads(WB_REASON_VMSCAN);
+               /*
+                * For cgroupv1 dirty throttling is achieved by waking up
+                * the kernel flusher here and later waiting on folios
+                * which are in writeback to finish (see shrink_folio_list()).
+                *
+                * Flusher may not be able to issue writeback quickly
+                * enough for cgroupv1 writeback throttling to work
+                * on a large system.
+                */
+               if (!writeback_throttling_sane(sc))
+                       reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK);
+       }
 
        sc->nr.dirty += stat.nr_dirty;
        sc->nr.congested += stat.nr_congested;