* [PATCH] mm: stricter check on THP migration entry
@ 2022-06-18 7:32 Miaohe Lin
2022-06-20 4:48 ` Matthew Wilcox
0 siblings, 1 reply; 3+ messages in thread
From: Miaohe Lin @ 2022-06-18 7:32 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, linmiaohe
When VM_BUG_ON check for THP migration entry, the existing code only check
thp_migration_supported case, but not for !thp_migration_supported case.
If !thp_migration_supported() and !pmd_present(), the original code may
dead loop in theory. To make the VM_BUG_ON check more consistent, we need
to catch both cases.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/memory.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index fee2884481f2..6a9a17c7f58a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5043,10 +5043,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
barrier();
if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
- VM_BUG_ON(thp_migration_supported() &&
- !is_pmd_migration_entry(vmf.orig_pmd));
- if (is_pmd_migration_entry(vmf.orig_pmd))
- pmd_migration_entry_wait(mm, vmf.pmd);
+ VM_BUG_ON(!thp_migration_supported() ||
+ !is_pmd_migration_entry(vmf.orig_pmd));
+ pmd_migration_entry_wait(mm, vmf.pmd);
return 0;
}
if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
--
2.23.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] mm: stricter check on THP migration entry
2022-06-18 7:32 [PATCH] mm: stricter check on THP migration entry Miaohe Lin
@ 2022-06-20 4:48 ` Matthew Wilcox
2022-06-20 6:38 ` Miaohe Lin
0 siblings, 1 reply; 3+ messages in thread
From: Matthew Wilcox @ 2022-06-20 4:48 UTC (permalink / raw)
To: Miaohe Lin; +Cc: akpm, linux-mm, linux-kernel
On Sat, Jun 18, 2022 at 03:32:43PM +0800, Miaohe Lin wrote:
> When VM_BUG_ON check for THP migration entry, the existing code only check
> thp_migration_supported case, but not for !thp_migration_supported case.
> If !thp_migration_supported() and !pmd_present(), the original code may
> dead loop in theory. To make the VM_BUG_ON check more consistent, we need
> to catch both cases.
This patch makes no sense to me.
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> mm/memory.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index fee2884481f2..6a9a17c7f58a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5043,10 +5043,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
>
> barrier();
> if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
> - VM_BUG_ON(thp_migration_supported() &&
> - !is_pmd_migration_entry(vmf.orig_pmd));
> - if (is_pmd_migration_entry(vmf.orig_pmd))
> - pmd_migration_entry_wait(mm, vmf.pmd);
> + VM_BUG_ON(!thp_migration_supported() ||
> + !is_pmd_migration_entry(vmf.orig_pmd));
> + pmd_migration_entry_wait(mm, vmf.pmd);
> return 0;
> }
> if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
> --
> 2.23.0
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm: stricter check on THP migration entry
2022-06-20 4:48 ` Matthew Wilcox
@ 2022-06-20 6:38 ` Miaohe Lin
0 siblings, 0 replies; 3+ messages in thread
From: Miaohe Lin @ 2022-06-20 6:38 UTC (permalink / raw)
To: Matthew Wilcox; +Cc: akpm, linux-mm, linux-kernel
On 2022/6/20 12:48, Matthew Wilcox wrote:
> On Sat, Jun 18, 2022 at 03:32:43PM +0800, Miaohe Lin wrote:
>> When VM_BUG_ON check for THP migration entry, the existing code only check
>> thp_migration_supported case, but not for !thp_migration_supported case.
>> If !thp_migration_supported() and !pmd_present(), the original code may
>> dead loop in theory. To make the VM_BUG_ON check more consistent, we need
>> to catch both cases.
>
> This patch makes no sense to me.
Could you please explain it more? This patch is inspired by below commit indeed:
28b0ee3fb350 ("mm/gup.c: stricter check on THP migration entry during follow_pmd_mask").
Thanks.
>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>> mm/memory.c | 7 +++----
>> 1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index fee2884481f2..6a9a17c7f58a 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -5043,10 +5043,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
>>
>> barrier();
>> if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
>> - VM_BUG_ON(thp_migration_supported() &&
>> - !is_pmd_migration_entry(vmf.orig_pmd));
>> - if (is_pmd_migration_entry(vmf.orig_pmd))
>> - pmd_migration_entry_wait(mm, vmf.pmd);
>> + VM_BUG_ON(!thp_migration_supported() ||
>> + !is_pmd_migration_entry(vmf.orig_pmd));
>> + pmd_migration_entry_wait(mm, vmf.pmd);
>> return 0;
>> }
>> if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
>> --
>> 2.23.0
>>
>>
>
> .
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-06-20 6:38 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-06-18 7:32 [PATCH] mm: stricter check on THP migration entry Miaohe Lin
2022-06-20 4:48 ` Matthew Wilcox
2022-06-20 6:38 ` Miaohe Lin
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