diff mbox series

[Resend,2/6] mm/memcg: remove useless check on page->mem_cgroup

Message ID 1597144232-11370-2-git-send-email-alex.shi@linux.alibaba.com (mailing list archive)
State New, archived
Headers show
Series [Resend,1/6] mm/memcg: warning on !memcg after readahead page charged | expand

Commit Message

Alex Shi Aug. 11, 2020, 11:10 a.m. UTC 
If we disabled memcg by cgroup_disable=memory, the swap charges are
still called. Let's return from the funcs earlier and keep WARN_ON
monitor.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Michal Hocko Aug. 11, 2020, 11:30 a.m. UTC | #1 
subject line looks like a left over. It doesn't match the path. Did you
mean
memcg: bail out early from swap accounting when memcg is disabled?

Btw. if this patch was first in the series then you wouldn't need to
mention the warnings that would trigger based on your previous patch.
I am fine with both ways but mentioning the warning is usefule.

On Tue 11-08-20 19:10:28, Alex Shi wrote:
> If we disabled memcg by cgroup_disable=memory, the swap charges are
> still called. Let's return from the funcs earlier and keep WARN_ON
> monitor.
> 
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Reviewed-by: Roman Gushchin <guro@fb.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  mm/memcontrol.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 299382fc55a9..419cf565f40b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>  	VM_BUG_ON_PAGE(PageLRU(page), page);
>  	VM_BUG_ON_PAGE(page_count(page), page);
>  
> +	if (mem_cgroup_disabled())
> +		return;
> +
>  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return;
>  
> @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
>  	struct mem_cgroup *memcg;
>  	unsigned short oldid;
>  
> +	if (mem_cgroup_disabled())
> +		return 0;
> +
>  	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return 0;
>  
> -- 
> 1.8.3.1
Alex Shi Aug. 11, 2020, 12:42 p.m. UTC | #2 
在 2020/8/11 下午7:30, Michal Hocko 写道:
> subject line looks like a left over. It doesn't match the path. Did you
> mean
> memcg: bail out early from swap accounting when memcg is disabled?

It's much better, Thanks for correction!

> 
> Btw. if this patch was first in the series then you wouldn't need to
> mention the warnings that would trigger based on your previous patch.
> I am fine with both ways but mentioning the warning is usefule.

Right. but the patch is very simple,  w/o warning message doesn't cuase trouble.
So, removing the 'and keep WARN_ON monitor' make sense too.

Do I need a resend for the commit log change?

Thanks a lot!
Alex

> 
> On Tue 11-08-20 19:10:28, Alex Shi wrote:
>> If we disabled memcg by cgroup_disable=memory, the swap charges are
>> still called. Let's return from the funcs earlier and keep WARN_ON
>> monitor.
>>
>> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
>> Reviewed-by: Roman Gushchin <guro@fb.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: cgroups@vger.kernel.org
>> Cc: linux-mm@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> ---
>>  mm/memcontrol.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 299382fc55a9..419cf565f40b 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>>  	VM_BUG_ON_PAGE(PageLRU(page), page);
>>  	VM_BUG_ON_PAGE(page_count(page), page);
>>  
>> +	if (mem_cgroup_disabled())
>> +		return;
>> +
>>  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
>>  		return;
>>  
>> @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
>>  	struct mem_cgroup *memcg;
>>  	unsigned short oldid;
>>  
>> +	if (mem_cgroup_disabled())
>> +		return 0;
>> +
>>  	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
>>  		return 0;
>>  
>> -- 
>> 1.8.3.1
>
Alex Shi Aug. 11, 2020, 12:54 p.m. UTC | #3 
From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed, 5 Aug 2020 21:02:30 +0800
Subject: [PATCH 2/6] memcg: bail out early from swap accounting when memcg is
 disabled

If we disabled memcg by cgroup_disable=memory, the swap charges are
still called. Let's return from the funcs earlier.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
@@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
+	if (mem_cgroup_disabled())
+		return 0;
+
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
Michal Hocko Aug. 11, 2020, 1:56 p.m. UTC | #4 
On Tue 11-08-20 20:54:18, Alex Shi wrote:
> >From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@linux.alibaba.com>
> Date: Wed, 5 Aug 2020 21:02:30 +0800
> Subject: [PATCH 2/6] memcg: bail out early from swap accounting when memcg is
>  disabled
> 
> If we disabled memcg by cgroup_disable=memory, the swap charges are
> still called. Let's return from the funcs earlier.

They are not, are they? page->memcg will be NULL and so the charge is
skipped and that will trigger a warning with your current ordering.

Let me repeat again. Either you put it first in the series and argue
that we can bail out early or keep the ordering then this makes sure the
warning doesn't trigger.

> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Reviewed-by: Roman Gushchin <guro@fb.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  mm/memcontrol.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 299382fc55a9..419cf565f40b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>  	VM_BUG_ON_PAGE(PageLRU(page), page);
>  	VM_BUG_ON_PAGE(page_count(page), page);
>  
> +	if (mem_cgroup_disabled())
> +		return;
> +
>  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return;
>  
> @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
>  	struct mem_cgroup *memcg;
>  	unsigned short oldid;
>  
> +	if (mem_cgroup_disabled())
> +		return 0;
> +
>  	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return 0;
>  
> -- 
> 1.8.3.1
Alex Shi Aug. 12, 2020, 3:25 a.m. UTC | #5 
在 2020/8/11 下午9:56, Michal Hocko 写道:
> On Tue 11-08-20 20:54:18, Alex Shi wrote:
>> >From beeac61119ab39b1869c520c0f272fb8bab93765 Mon Sep 17 00:00:00 2001
>> From: Alex Shi <alex.shi@linux.alibaba.com>
>> Date: Wed, 5 Aug 2020 21:02:30 +0800
>> Subject: [PATCH 2/6] memcg: bail out early from swap accounting when memcg is
>>  disabled>>
>> If we disabled memcg by cgroup_disable=memory, the swap charges are
>> still called. Let's return from the funcs earlier.
> They are not, are they? page->memcg will be NULL and so the charge is
> skipped and that will trigger a warning with your current ordering.

Hi Michal,

Thanks for comment! Looks like we both agree the memcg wasn't charged, but funcs
just are called. :)
  
> 
> Let me repeat again. Either you put it first in the series and argue
> that we can bail out early or keep the ordering then this makes sure the
> warning doesn't trigger.
> 

Is the following commit log fine?

Thanks!
Alex

From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed, 5 Aug 2020 21:02:30 +0800
Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg
 is disabled

If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL
and so the charge is skipped and that will trigger a warning like below.
Let's return from the funcs earlier.

 ---[ end trace f1f34bfc3b32ed2f ]---
 anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked)
 raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
 raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
 page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
@@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
+	if (mem_cgroup_disabled())
+		return 0;
+
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
Michal Hocko Aug. 13, 2020, 6:20 a.m. UTC | #6 
On Wed 12-08-20 11:25:53, Alex Shi wrote:
> >From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@linux.alibaba.com>
> Date: Wed, 5 Aug 2020 21:02:30 +0800
> Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg
>  is disabled
> 
> If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL
> and so the charge is skipped and that will trigger a warning like below.
> Let's return from the funcs earlier.
> 
>  ---[ end trace f1f34bfc3b32ed2f ]---
>  anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked)
>  raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
>  raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
>  page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)

Yes this is better. It would be even more informative if you added the
backtrace.
 
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Reviewed-by: Roman Gushchin <guro@fb.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  mm/memcontrol.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 299382fc55a9..419cf565f40b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>  	VM_BUG_ON_PAGE(PageLRU(page), page);
>  	VM_BUG_ON_PAGE(page_count(page), page);
>  
> +	if (mem_cgroup_disabled())
> +		return;
> +
>  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return;
>  
> @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
>  	struct mem_cgroup *memcg;
>  	unsigned short oldid;
>  
> +	if (mem_cgroup_disabled())
> +		return 0;
> +
>  	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
>  		return 0;
>  
> -- 
> 1.8.3.1
Alex Shi Aug. 13, 2020, 9:45 a.m. UTC | #7 
在 2020/8/13 下午2:20, Michal Hocko 写道:
> On Wed 12-08-20 11:25:53, Alex Shi wrote:
>> >From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001
>> From: Alex Shi <alex.shi@linux.alibaba.com>
>> Date: Wed, 5 Aug 2020 21:02:30 +0800
>> Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg
>>  is disabled
>>
>> If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL
>> and so the charge is skipped and that will trigger a warning like below.
>> Let's return from the funcs earlier.
>>
>>  ---[ end trace f1f34bfc3b32ed2f ]---
>>  anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked)
>>  raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
>>  raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
>>  page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
> 
> Yes this is better. It would be even more informative if you added the
> backtrace.

The stack is a bit long.
I still don't know where cause the asm_exc_page_fault? And seems the vma is from
kernel not user.

From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@linux.alibaba.com>
Date: Wed, 5 Aug 2020 21:02:30 +0800
Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg
 is disabled

If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL
and so the charge is skipped and that will trigger a warning like below.
Let's return from the funcs earlier.

 anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked)
 raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
 raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
 page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
...
 RIP: 0010:vprintk_emit+0x1f7/0x260
 Code: 00 84 d2 74 72 0f b6 15 27 58 64 01 48 c7 c0 00 d4 72 82 84 d2 74 09 f3 90 0f b6 10 84 d2 75 f7 e8 de 0d 00 00 4c 89 e7 57 9d <0f> 1f 44 00 00 e9 62 ff ff ff 80 3d 88 c9 3a 01 00 0f 85 54 fe ff
 RSP: 0018:ffffc9000faab358 EFLAGS: 00000202
 RAX: ffffffff8272d400 RBX: 000000000000005e RCX: ffff88afd80d0040
 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000202
 RBP: ffffc9000faab3a8 R08: ffffffff8272d440 R09: 0000000000022480
 R10: 00120c77be68bfac R11: 0000000000cd7568 R12: 0000000000000202
 R13: 0057ffffc0080005 R14: ffffffff820a0130 R15: ffffc9000faab3e8
 ? vprintk_emit+0x140/0x260
 vprintk_default+0x1a/0x20
 vprintk_func+0x4f/0xc4
 ? vprintk_func+0x4f/0xc4
 printk+0x53/0x6a
 ? xas_load+0xc/0x80
 __dump_page.cold.6+0xff/0x4ee
 ? xas_init_marks+0x23/0x50
 ? xas_store+0x30/0x40
 ? free_swap_slot+0x43/0xd0
 ? put_swap_page+0x119/0x320
 ? update_load_avg+0x82/0x580
 dump_page+0x9/0xb
 mem_cgroup_try_charge_swap+0x16e/0x1d0
 get_swap_page+0x130/0x210
 add_to_swap+0x41/0xc0
 shrink_page_list+0x99e/0xdf0
 shrink_inactive_list+0x199/0x360
 shrink_lruvec+0x40d/0x650
 ? _cond_resched+0x14/0x30
 ? _cond_resched+0x14/0x30
 shrink_node+0x226/0x6e0
 do_try_to_free_pages+0xd0/0x400
 try_to_free_pages+0xef/0x130
 __alloc_pages_slowpath.constprop.127+0x38d/0xbd0
 ? ___slab_alloc+0x31d/0x6f0
 __alloc_pages_nodemask+0x27f/0x2c0
 alloc_pages_vma+0x75/0x220
 shmem_alloc_page+0x46/0x90
 ? release_pages+0x1ae/0x410
 shmem_alloc_and_acct_page+0x77/0x1c0
 shmem_getpage_gfp+0x162/0x910
 shmem_fault+0x74/0x210
 ? filemap_map_pages+0x29c/0x410
 __do_fault+0x37/0x190
 handle_mm_fault+0x120a/0x1770
 exc_page_fault+0x251/0x450
 ? asm_exc_page_fault+0x8/0x30
 asm_exc_page_fault+0x1e/0x30

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
@@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
+	if (mem_cgroup_disabled())
+		return 0;
+
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
Michal Hocko Aug. 13, 2020, 11:01 a.m. UTC | #8 
On Thu 13-08-20 17:45:19, Alex Shi wrote:
> 
> 
> 在 2020/8/13 下午2:20, Michal Hocko 写道:
> > On Wed 12-08-20 11:25:53, Alex Shi wrote:
> >> >From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001
> >> From: Alex Shi <alex.shi@linux.alibaba.com>
> >> Date: Wed, 5 Aug 2020 21:02:30 +0800
> >> Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg
> >>  is disabled
> >>
> >> If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL
> >> and so the charge is skipped and that will trigger a warning like below.
> >> Let's return from the funcs earlier.
> >>
> >>  ---[ end trace f1f34bfc3b32ed2f ]---
> >>  anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked)
> >>  raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
> >>  raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
> >>  page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
> > 
> > Yes this is better. It would be even more informative if you added the
> > backtrace.
> 
> The stack is a bit long.

This doesn't matter. It is informative and potentially useful for future
reference.

Thanks!
diff mbox series

Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@  void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return;
 
@@ -7163,6 +7166,9 @@  int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
+	if (mem_cgroup_disabled())
+		return 0;
+
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;