* [PATCH] mm/page_alloc.c: avoid inheritting current's flags when invoked in interrupt
@ 2020-09-15 7:56 yanfei.xu
2020-09-16 1:17 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: yanfei.xu @ 2020-09-15 7:56 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel
From: Yanfei Xu <yanfei.xu@windriver.com>
alloc_mask shouldn't inherit the current task's flags when
__alloc_pages_nodemask is invoked in interrupt.
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
---
mm/page_alloc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fab5e97dc9ca..388b587b35a8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4889,7 +4889,8 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
* from a particular context which has been marked by
* memalloc_no{fs,io}_{save,restore}.
*/
- alloc_mask = current_gfp_context(gfp_mask);
+ if (!in_interrupt())
+ alloc_mask = current_gfp_context(gfp_mask);
ac.spread_dirty_pages = false;
/*
--
2.18.2
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm/page_alloc.c: avoid inheritting current's flags when invoked in interrupt
2020-09-15 7:56 [PATCH] mm/page_alloc.c: avoid inheritting current's flags when invoked in interrupt yanfei.xu
@ 2020-09-16 1:17 ` Andrew Morton
2020-09-16 3:47 ` Xu, Yanfei
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2020-09-16 1:17 UTC (permalink / raw)
To: yanfei.xu; +Cc: linux-mm, linux-kernel
On Tue, 15 Sep 2020 15:56:35 +0800 <yanfei.xu@windriver.com> wrote:
> From: Yanfei Xu <yanfei.xu@windriver.com>
>
> alloc_mask shouldn't inherit the current task's flags when
> __alloc_pages_nodemask is invoked in interrupt.
>
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4889,7 +4889,8 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
> * from a particular context which has been marked by
> * memalloc_no{fs,io}_{save,restore}.
> */
> - alloc_mask = current_gfp_context(gfp_mask);
> + if (!in_interrupt())
> + alloc_mask = current_gfp_context(gfp_mask);
> ac.spread_dirty_pages = false;
>
> /*
hm, yes, and perhaps other callsites in page_alloc.c.
I assume this doesn't actually make any runtime difference? Because
gfp_mask in interrupt contexts isn't going to have __GFP_IO or __GFP_FS
anyway.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm/page_alloc.c: avoid inheritting current's flags when invoked in interrupt
2020-09-16 1:17 ` Andrew Morton
@ 2020-09-16 3:47 ` Xu, Yanfei
0 siblings, 0 replies; 3+ messages in thread
From: Xu, Yanfei @ 2020-09-16 3:47 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, linux-kernel
On 9/16/20 9:17 AM, Andrew Morton wrote:
> On Tue, 15 Sep 2020 15:56:35 +0800 <yanfei.xu@windriver.com> wrote:
>
>> From: Yanfei Xu <yanfei.xu@windriver.com>
>>
>> alloc_mask shouldn't inherit the current task's flags when
>> __alloc_pages_nodemask is invoked in interrupt.
>>
>> ...
>>
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -4889,7 +4889,8 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>> * from a particular context which has been marked by
>> * memalloc_no{fs,io}_{save,restore}.
>> */
>> - alloc_mask = current_gfp_context(gfp_mask);
>> + if (!in_interrupt())
>> + alloc_mask = current_gfp_context(gfp_mask);
>> ac.spread_dirty_pages = false;
>>
>> /*
>
> hm, yes, and perhaps other callsites in page_alloc.c.
>
> I assume this doesn't actually make any runtime difference? Because
> gfp_mask in interrupt contexts isn't going to have __GFP_IO or __GFP_FS
> anyway.
>
Thanks for your reply!
Yes, It doesn't make any runtime difference. Theoretically, GPF_ATOMIC
or GFP_NOWAIT should be used in interrupt context for allocate pages, so
that gfp_mask isn't going to have __GFP_IO or __GFP_FS.
But if somebody use wrong gfp_masks, __GFP_IO or __GFP_FS will be
introduced, with the process interrupted has PF_MEMALLOC_NOIO or
PF_MEMALLOC_NOFS, current_gfp_context may help to hide these wrong
usages. I don't think it is the original purpose of that piece of
codes.
And how about add BUG_ON or WARN_ON to figure out the situation which
introduce __GFP_IO or __GFP_FS in interrupt context?
Regards,
Yanfei
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-09-15 7:56 [PATCH] mm/page_alloc.c: avoid inheritting current's flags when invoked in interrupt yanfei.xu
2020-09-16 1:17 ` Andrew Morton
2020-09-16 3:47 ` Xu, Yanfei
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