[PATCH] mm,page_alloc: softlockup on warn_alloc on

[wang Yu <yuwang668899@gmail.com>]

From: "yuwang.yuwang" <yuwang.yuwang@alibaba-inc.com>

I found a softlockup when running some stress testcase in 4.9.x,
but i think the mainline have the same problem.

call trace:
[365724.502896] NMI watchdog: BUG: soft lockup - CPU#31 stuck for 22s!
[jbd2/sda3-8:1164]
...
...
[365724.503258] Call Trace:
[365724.503260]  [<ffffffff811ace5f>] warn_alloc+0x13f/0x170
[365724.503264]  [<ffffffff811ad8c2>] __alloc_pages_slowpath+0x9b2/0xc10
[365724.503265]  [<ffffffff811add43>] __alloc_pages_nodemask+0x223/0x2a0
[365724.503268]  [<ffffffff811fe838>] alloc_pages_current+0x88/0x120
[365724.503270]  [<ffffffff811a3644>] __page_cache_alloc+0xb4/0xc0
[365724.503272]  [<ffffffff811a49e9>] pagecache_get_page+0x59/0x230
[365724.503275]  [<ffffffff8126b2db>] __getblk_gfp+0xfb/0x2f0
[365724.503281]  [<ffffffffa00f9cee>]
jbd2_journal_get_descriptor_buffer+0x5e/0xe0 [jbd2]
[365724.503286]  [<ffffffffa00f2a01>]
jbd2_journal_commit_transaction+0x901/0x1880 [jbd2]
[365724.503291]  [<ffffffff8102d6a5>] ? __switch_to+0x215/0x730
[365724.503294]  [<ffffffff810f962d>] ? lock_timer_base+0x7d/0xa0
[365724.503298]  [<ffffffffa00f7cda>] kjournald2+0xca/0x260 [jbd2]
[365724.503300]  [<ffffffff810cfb00>] ? prepare_to_wait_event+0xf0/0xf0
[365724.503304]  [<ffffffffa00f7c10>] ? commit_timeout+0x10/0x10 [jbd2]
[365724.503307]  [<ffffffff810a8d66>] kthread+0xe6/0x100
[365724.503309]  [<ffffffff810a8c80>] ? kthread_park+0x60/0x60
[365724.503313]  [<ffffffff816f3795>] ret_from_fork+0x25/0x30

we can limit the warn_alloc caller to workaround it.
__alloc_pages_slowpath only call once warn_alloc each time.

Signed-off-by: yuwang.yuwang <yuwang.yuwang@alibaba-inc.com>
Suggested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
---
 mm/page_alloc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2abf8d5..8b86686 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3525,6 +3525,7 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
 	unsigned long alloc_start = jiffies;
 	unsigned int stall_timeout = 10 * HZ;
 	unsigned int cpuset_mems_cookie;
+	static unsigned long stall_warn_lock;
 
 	/*
 	 * In the slowpath, we sanity check order to avoid ever trying to
@@ -3698,11 +3699,13 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
 		goto nopage;
 
 	/* Make sure we know about allocations which stall for too long */
-	if (time_after(jiffies, alloc_start + stall_timeout)) {
+	if (time_after(jiffies, alloc_start + stall_timeout) &&
+		!test_and_set_bit_lock(0, &stall_warn_lock)) {
 		warn_alloc(gfp_mask,
 			"page allocation stalls for %ums, order:%u",
 			jiffies_to_msecs(jiffies-alloc_start), order);
-		stall_timeout += 10 * HZ;
+		stall_timeout = jiffies - alloc_start + 10 * HZ;
+		clear_bit_unlock(0, &stall_warn_lock);
 	}
 
 	if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags,
-- 
1.8.3.1

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