* [PATCH] mm page_fault: Reduce code complexity
@ 2020-05-28 11:01 hui yang
2020-05-28 11:45 ` Matthew Wilcox
0 siblings, 1 reply; 2+ messages in thread
From: hui yang @ 2020-05-28 11:01 UTC (permalink / raw)
To: willy; +Cc: akpm, linux-mm, YangHui
From: YangHui <yanghui.def@gmail.com>
if pte_alloc_one failed alloc a page, do_fault_around will return 0.
and it will come into __do_fault(), it also pte_alloc_one a page.
in __do_fault and do_fault_around, pte_alloc_one did the same thing,
if do_fault_around alloc page filed,we just let it return. there is
no need to come into __do_fault to do repetitive pte_alloc_one.
Signed-off-by: YangHui <yanghui.def@gmail.com>
---
mm/memory.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index f703fe8..a2d50a9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3799,8 +3799,10 @@ static vm_fault_t do_fault_around(struct vm_fault *vmf)
if (pmd_none(*vmf->pmd)) {
vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
- if (!vmf->prealloc_pte)
+ if (!vmf->prealloc_pte) {
+ ret = VM_FAULT_OOM;
goto out;
+ }
smp_wmb(); /* See comment in __pte_alloc() */
}
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] mm page_fault: Reduce code complexity
2020-05-28 11:01 [PATCH] mm page_fault: Reduce code complexity hui yang
@ 2020-05-28 11:45 ` Matthew Wilcox
0 siblings, 0 replies; 2+ messages in thread
From: Matthew Wilcox @ 2020-05-28 11:45 UTC (permalink / raw)
To: hui yang; +Cc: akpm, linux-mm
On Thu, May 28, 2020 at 07:01:39PM +0800, hui yang wrote:
> From: YangHui <yanghui.def@gmail.com>
>
> if pte_alloc_one failed alloc a page, do_fault_around will return 0.
> and it will come into __do_fault(), it also pte_alloc_one a page.
> in __do_fault and do_fault_around, pte_alloc_one did the same thing,
> if do_fault_around alloc page filed,we just let it return. there is
> no need to come into __do_fault to do repetitive pte_alloc_one.
This really isn't "Reduce code complexity" though. It's "Fail early
when memory allocation fails". And, honestly, I don't see the point
of doing this. You've optimised an incredibly rare failure path.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2020-05-28 11:01 [PATCH] mm page_fault: Reduce code complexity hui yang
2020-05-28 11:45 ` Matthew Wilcox
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