Re: [PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to __tlb_remove_table()

On 2025/1/7 17:57, Kevin Brodsky wrote:
> On 06/01/2025 04:49, Qi Zheng wrote:
>> [...]
>>
>>> Once this is done, we should be able to replace all those confusing
>>> calls to tlb_remove_page() on PTPs with tlb_remove_table() and remove
>>> the explicit call to pagetable_dtor(). AIUI this is essentially what
>>> Peter suggested on v3 [2].
>>
>> Since this patch series is mainly for bug fix, I think that these things
>> can be done in separate patch series later.
> 
> Sure that's fair.
> 
>>
>>>
>>> [...]
>>>
>>>> Or can we just not let tlb_remove_table() fall back to
>>>> tlb_remove_page()? Like the following:
>>>>
>>>> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
>>>> index a59205863f431..354ffaa4bd120 100644
>>>> --- a/include/asm-generic/tlb.h
>>>> +++ b/include/asm-generic/tlb.h
>>>> @@ -195,8 +195,6 @@
>>>>     *  various ptep_get_and_clear() functions.
>>>>     */
>>>>
>>>> -#ifdef CONFIG_MMU_GATHER_TABLE_FREE
>>>> -
>>>>    struct mmu_table_batch {
>>>>    #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
>>>>           struct rcu_head         rcu;
>>>> @@ -219,16 +217,6 @@ static inline void __tlb_remove_table(void *table)
>>>>
>>>>    extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
>>>>
>>>> -#else /* !CONFIG_MMU_GATHER_HAVE_TABLE_FREE */
>>>> -
>>>> -/*
>>>> - * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have
>>>> page based
>>>> - * page directories and we can use the normal page batching to free
>>>> them.
>>>> - */
>>>> -#define tlb_remove_table(tlb, page) tlb_remove_page((tlb), (page))
>>>
>>> We still need a different implementation of tlb_remove_table() in this
>>> case. We could define it inline here:
>>>
>>> static inline void tlb_remove_table(struct mmu_gather *tlb, void *table)
>>> {
>>>       struct page *page = table;
>>>
>>>       pagetable_dtor(page_ptdesc(page));
>>>       tlb_remove_page(page);
>>> }
>>
>> Right. As I said above, will add this to the updated patch #8.
> 
> I think it would be preferable to make it a standalone patch, because
> this is a change to generic code that could in principle impact other
> arch's too.

Agree, I have done that:

```
Author: Qi Zheng <[email protected]>
Date:   Fri Dec 13 17:13:48 2024 +0800

     mm: pgtable: completely move pagetable_dtor() to generic 
tlb_remove_table()

     For the generic tlb_remove_table(), it is implemented in the 
following two
     forms:

     1) CONFIG_MMU_GATHER_TABLE_FREE is enabled

     tlb_remove_table
     --> generic __tlb_remove_table()

     2) CONFIG_MMU_GATHER_TABLE_FREE is disabled

     tlb_remove_table
     --> tlb_remove_page

     For case 1), the pagetable_dtor() has already been moved to generic
     __tlb_remove_table().

     For case 2), now only arm will call 
tlb_remove_table()/tlb_remove_ptdesc()
     when CONFIG_MMU_GATHER_TABLE_FREE is disabled. Let's move 
pagetable_dtor()
     completely to generic tlb_remove_table(), so that the architectures can
     follow more easily.

     Signed-off-by: Qi Zheng <[email protected]>

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index b8eebdb598631..ea4fbe7b17f6f 100644
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -34,10 +34,6 @@ __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, 
unsigned long addr)
  {
         struct ptdesc *ptdesc = page_ptdesc(pte);

-#ifndef CONFIG_MMU_GATHER_TABLE_FREE
-       pagetable_dtor(ptdesc);
-#endif
-
  #ifndef CONFIG_ARM_LPAE
         /*
          * With the classic ARM MMU, a pte page has two corresponding pmd
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 69de47c7ef3c5..53ae7748f555b 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -220,14 +220,20 @@ static inline void __tlb_remove_table(void *table)

  extern void tlb_remove_table(struct mmu_gather *tlb, void *table);

-#else /* !CONFIG_MMU_GATHER_HAVE_TABLE_FREE */
+#else /* !CONFIG_MMU_GATHER_TABLE_FREE */

+static inline void tlb_remove_page(struct mmu_gather *tlb, struct page 
*page);
  /*
   * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have 
page based
   * page directories and we can use the normal page batching to free them.
   */
-#define tlb_remove_table(tlb, page) tlb_remove_page((tlb), (page))
+static inline void tlb_remove_table(struct mmu_gather *tlb, void *table)
+{
+       struct page *page = (struct page *)table;

+       pagetable_dtor(page_ptdesc(page));
+       tlb_remove_page(tlb, page);
+}
  #endif /* CONFIG_MMU_GATHER_TABLE_FREE */

  #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
```

and will send v5 later.

Thanks!

> 
> - Kevin