Factor pageset_set_high_and_batch() (which contains all needed logic too
set a pageset's ->high and ->batch inrespective of system state) out of
zone_pageset_init(), which avoids us calling pageset_init(), and
unsafely blowing away a pageset at runtime (leaked pages and
potentially some funky allocations would be the result) when memory
hotplug is triggered.
Signed-off-by: Cody P Schafer <[email protected]>
---
Unless memory hotplug is being triggered on boot, this should *not* be cause of Valdis
Kletnieks' reported bug in -next:
"next-20130607 BUG: Bad page state in process systemd pfn:127643"
---
mm/page_alloc.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 18102e1..f62c7ac 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4111,11 +4111,9 @@ static void pageset_set_high(struct per_cpu_pageset *p,
pageset_update(&p->pcp, high, batch);
}
-static void __meminit zone_pageset_init(struct zone *zone, int cpu)
+static void __meminit pageset_set_high_and_batch(struct zone *zone,
+ struct per_cpu_pageset *pcp)
{
- struct per_cpu_pageset *pcp = per_cpu_ptr(zone->pageset, cpu);
-
- pageset_init(pcp);
if (percpu_pagelist_fraction)
pageset_set_high(pcp,
(zone->managed_pages /
@@ -4124,6 +4122,14 @@ static void __meminit zone_pageset_init(struct zone *zone, int cpu)
pageset_set_batch(pcp, zone_batchsize(zone));
}
+static void __meminit zone_pageset_init(struct zone *zone, int cpu)
+{
+ struct per_cpu_pageset *pcp = per_cpu_ptr(zone->pageset, cpu);
+
+ pageset_init(pcp);
+ pageset_set_high_and_batch(zone, pcp);
+}
+
static void __meminit setup_zone_pageset(struct zone *zone)
{
int cpu;
@@ -6173,7 +6179,8 @@ void __meminit zone_pcp_update(struct zone *zone)
unsigned cpu;
mutex_lock(&pcp_batch_high_lock);
for_each_possible_cpu(cpu)
- zone_pageset_init(zone, cpu);
+ pageset_set_high_and_batch(zone,
+ per_cpu_ptr(zone->pageset, cpu));
mutex_unlock(&pcp_batch_high_lock);
}
#endif
--
1.8.3
On Tue, 11 Jun 2013 15:12:59 -0700 Cody P Schafer <[email protected]> wrote:
> Factor pageset_set_high_and_batch() (which contains all needed logic too
> set a pageset's ->high and ->batch inrespective of system state) out of
> zone_pageset_init(), which avoids us calling pageset_init(), and
> unsafely blowing away a pageset at runtime (leaked pages and
> potentially some funky allocations would be the result) when memory
> hotplug is triggered.
This changelog is pretty screwed up :( It tells us what the patch does
but not why it does it.
> Signed-off-by: Cody P Schafer <[email protected]>
> ---
>
> Unless memory hotplug is being triggered on boot, this should *not* be cause of Valdis
> Kletnieks' reported bug in -next:
> "next-20130607 BUG: Bad page state in process systemd pfn:127643"
And this addendum appears to hint at the info we need.
Please, send a new changelog? That should include a description of the
user-visible effects of the bug which is being fixed, a description of
why it occurs and a description of how it was fixed. It would also be
helpful if you can identify which kernel version(s) need the fix.
Also, a Reported-by:Valdis would be appropriate.
Thanks.
On 06/12/2013 02:20 PM, Andrew Morton wrote:
> On Tue, 11 Jun 2013 15:12:59 -0700 Cody P Schafer <[email protected]> wrote:
>
>> Factor pageset_set_high_and_batch() (which contains all needed logic too
>> set a pageset's ->high and ->batch inrespective of system state) out of
>> zone_pageset_init(), which avoids us calling pageset_init(), and
>> unsafely blowing away a pageset at runtime (leaked pages and
>> potentially some funky allocations would be the result) when memory
>> hotplug is triggered.
>
> This changelog is pretty screwed up :( It tells us what the patch does
> but not why it does it.
>
It says why it does it, though perhaps a bit hidden:
> avoids us calling pageset_init(), and unsafely blowing away a pageset
>> Signed-off-by: Cody P Schafer <[email protected]>
>> ---
>>
>> Unless memory hotplug is being triggered on boot, this should *not* be cause of Valdis
>> Kletnieks' reported bug in -next:
>> "next-20130607 BUG: Bad page state in process systemd pfn:127643"
>
> And this addendum appears to hint at the info we need.
Note the *not*. I included this note only because I expected there would
be a question of whether Valdis's reported bug was caused by this. It
_isn't_. The bug this fix fixes is only triggered by memory_hotplug, and
Valdis's bug occurred on boot.
> Please, send a new changelog? That should include a description of the
> user-visible effects of the bug which is being fixed, a description of
> why it occurs and a description of how it was fixed.It would also be
> helpful if you can identify which kernel version(s) need the fix.
It's just a -mm issue. It was introduced by my patchset starting with
"mm/page_alloc: factor out setting of pcp->high and pcp->batch", where
the actual place the bug snuck in was "mm/page_alloc: in
zone_pcp_update(), uze zone_pageset_init()".
>
> Also, a Reported-by:Valdis would be appropriate.
>
I'm fine with adding it (I did take a look at my page_alloc.c changes
because he reported that bug), but as mentioned before, this fixes a
different bug.
Anyhow, a reorganized (and clearer) changelog with the same content follows:
---
mm/page_alloc: don't re-init pageset in zone_pcp_update()
When memory hotplug is triggered, we call pageset_init() on a
per-cpu-pageset which both contains pages and is in use, causing both
the leakage of those pages and (potentially) bad behaviour if a page is
allocated from the pageset while it is being cleared.
Avoid this by factoring pageset_set_high_and_batch() (which contains all
needed logic too set a pageset's ->high and ->batch inrespective of
system state), and using that instead of zone_pageset_init() in
zone_pcp_update().
Signed-off-by: Cody P Schafer <[email protected]>
> Anyhow, a reorganized (and clearer) changelog with the same content
> follows:
> ---
I made a few wording tweaks:
---
mm/page_alloc: don't re-init pageset in zone_pcp_update()
When memory hotplug is triggered, we call pageset_init() on
per-cpu-pagesets which both contain pages and are in use, causing both
the leakage of those pages and (potentially) bad behaviour if a page is
allocated from a pageset while it is being cleared.
Avoid this by factoring out pageset_set_high_and_batch() (which contains
all needed logic too set a pageset's ->high and ->batch inrespective of
system state) from zone_pageset_init() and using the new
pageset_set_high_and_batch() instead of zone_pageset_init() in
zone_pcp_update().
Signed-off-by: Cody P Schafer <[email protected]>