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Subject: Re: [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations
 __free_slab() invocations out of IRQ context
From:   Vlastimil Babka <vbabka@suse.cz>
To:     Qian Cai <quic_qiancai@quicinc.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Mike Galbraith <efault@gmx.de>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Mel Gorman <mgorman@techsingularity.net>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Jann Horn <jannh@google.com>
References: <20210805152000.12817-1-vbabka@suse.cz>
 <20210805152000.12817-30-vbabka@suse.cz>
 <0b36128c-3e12-77df-85fe-a153a714569b@quicinc.com>
 <50fe26ba-450b-af57-506d-438f67cfbce3@suse.cz>
Message-ID: <60e50d8c-ccfa-1036-5a03-2b1a9d25f958@suse.cz>
Date:   Wed, 11 Aug 2021 10:55:34 +0200
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On 8/10/21 4:33 PM, Vlastimil Babka wrote:
> On 8/9/21 3:41 PM, Qian Cai wrote:
> 
>>>  static void flush_all(struct kmem_cache *s)
>>>  {
>>> -	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1);
>>> +	struct slub_flush_work *sfw;
>>> +	unsigned int cpu;
>>> +
>>> +	mutex_lock(&flush_lock);
>> 
>> Vlastimil, taking the lock here could trigger a warning during memory offline/online due to the locking order:
>> 
>> slab_mutex -> flush_lock
> 
> Here's the full fixup, also incorporating Mike's fix. Thanks.
> 

One more fixup, sorry for the churn.
----8<----
From 7cfe3fb1bcd6e589199b10bef480ed097ba9de14 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@suse.cz>
Date: Wed, 11 Aug 2021 10:51:14 +0200
Subject: [PATCH] mm, slub: fix memory and cpu hotplug related lock ordering
 issues - fix

Make __kmem_cache_do_shrink static to silence "no previous prototype" warning.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 152487f84025..c9531e03addd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4393,7 +4393,7 @@ EXPORT_SYMBOL(kfree);
  * being allocated from last increasing the chance that the last objects
  * are freed in them.
  */
-int __kmem_cache_do_shrink(struct kmem_cache *s)
+static int __kmem_cache_do_shrink(struct kmem_cache *s)
 {
 	int node;
 	int i;
-- 
2.32.0