From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Fri, 25 Sep 2020 10:55:57 +0000 (+0200)
Subject: 5.4-stable patches
X-Git-Tag: v4.19.148~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f22defd571988547089d2c05b314d2bc228cef94;p=thirdparty%2Fkernel%2Fstable-queue.git

5.4-stable patches

added patches:
	mm-memcg-fix-memcg-reclaim-soft-lockup.patch
---

diff --git a/queue-5.4/mm-memcg-fix-memcg-reclaim-soft-lockup.patch b/queue-5.4/mm-memcg-fix-memcg-reclaim-soft-lockup.patch
new file mode 100644
index 00000000000..8f846da551d
--- /dev/null
+++ b/queue-5.4/mm-memcg-fix-memcg-reclaim-soft-lockup.patch
@@ -0,0 +1,70 @@
+From e3336cab2579012b1e72b5265adf98e2d6e244ad Mon Sep 17 00:00:00 2001
+From: Xunlei Pang <xlpang@linux.alibaba.com>
+Date: Fri, 4 Sep 2020 16:35:27 -0700
+Subject: mm: memcg: fix memcg reclaim soft lockup
+
+From: Xunlei Pang <xlpang@linux.alibaba.com>
+
+commit e3336cab2579012b1e72b5265adf98e2d6e244ad upstream.
+
+We've met softlockup with "CONFIG_PREEMPT_NONE=y", when the target memcg
+doesn't have any reclaimable memory.
+
+It can be easily reproduced as below:
+
+  watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204]
+  CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12
+  Call Trace:
+    shrink_lruvec+0x49f/0x640
+    shrink_node+0x2a6/0x6f0
+    do_try_to_free_pages+0xe9/0x3e0
+    try_to_free_mem_cgroup_pages+0xef/0x1f0
+    try_charge+0x2c1/0x750
+    mem_cgroup_charge+0xd7/0x240
+    __add_to_page_cache_locked+0x2fd/0x370
+    add_to_page_cache_lru+0x4a/0xc0
+    pagecache_get_page+0x10b/0x2f0
+    filemap_fault+0x661/0xad0
+    ext4_filemap_fault+0x2c/0x40
+    __do_fault+0x4d/0xf9
+    handle_mm_fault+0x1080/0x1790
+
+It only happens on our 1-vcpu instances, because there's no chance for
+oom reaper to run to reclaim the to-be-killed process.
+
+Add a cond_resched() at the upper shrink_node_memcgs() to solve this
+issue, this will mean that we will get a scheduling point for each memcg
+in the reclaimed hierarchy without any dependency on the reclaimable
+memory in that memcg thus making it more predictable.
+
+Suggested-by: Michal Hocko <mhocko@suse.com>
+Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Acked-by: Chris Down <chris@chrisdown.name>
+Acked-by: Michal Hocko <mhocko@suse.com>
+Acked-by: Johannes Weiner <hannes@cmpxchg.org>
+Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Julius Hemanth Pitti <jpitti@cisco.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ mm/vmscan.c |    8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+--- a/mm/vmscan.c
++++ b/mm/vmscan.c
+@@ -2775,6 +2775,14 @@ static bool shrink_node(pg_data_t *pgdat
+ 			unsigned long reclaimed;
+ 			unsigned long scanned;
+ 
++			/*
++			 * This loop can become CPU-bound when target memcgs
++			 * aren't eligible for reclaim - either because they
++			 * don't have any reclaimable pages, or because their
++			 * memory is explicitly protected. Avoid soft lockups.
++			 */
++			cond_resched();
++
+ 			switch (mem_cgroup_protected(root, memcg)) {
+ 			case MEMCG_PROT_MIN:
+ 				/*
diff --git a/queue-5.4/series b/queue-5.4/series
index cf65d446435..3801b93f2f6 100644
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -39,3 +39,4 @@ net-phy-avoid-npd-upon-phy_detach-when-driver-is-unbound.patch
 net-phy-do-not-warn-in-phy_stop-on-phy_down.patch
 net-qrtr-check-skb_put_padto-return-value.patch
 net-add-__must_check-to-skb_put_padto.patch
+mm-memcg-fix-memcg-reclaim-soft-lockup.patch