[PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[john.hubbard]

From: John Hubbard <jhubbard@nvidia.com>

For pages that were retained via get_user_pages*(), release those pages
via the new put_user_page*() routines, instead of via put_page() or
release_pages().

This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
("mm: introduce put_user_page*(), placeholder versions").

Note that this effectively changes the code's behavior in
mm_iommu_unpin(): it now ultimately calls set_page_dirty_lock(),
instead of set_page_dirty(). This is probably more accurate.

As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [1]

[1] https://lore.kernel.org/r/20190723153640.GB720@lst.de

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c    |  4 ++--
 arch/powerpc/kvm/book3s_64_mmu_radix.c | 19 ++++++++++++++-----
 arch/powerpc/kvm/e500_mmu.c            |  3 +--
 arch/powerpc/mm/book3s64/iommu_api.c   | 11 +++++------
 4 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 9a75f0e1933b..18646b738ce1 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -731,7 +731,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 		 * we have to drop the reference on the correct tail
 		 * page to match the get inside gup()
 		 */
-		put_page(pages[0]);
+		put_user_page(pages[0]);
 	}
 	return ret;
 
@@ -1206,7 +1206,7 @@ void kvmppc_unpin_guest_page(struct kvm *kvm, void *va, unsigned long gpa,
 	unsigned long gfn;
 	int srcu_idx;
 
-	put_page(page);
+	put_user_page(page);
 
 	if (!dirty)
 		return;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 2d415c36a61d..f53273fbfa2d 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -821,8 +821,12 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 	 */
 	if (!ptep) {
 		local_irq_enable();
-		if (page)
-			put_page(page);
+		if (page) {
+			if (upgrade_write)
+				put_user_page(page);
+			else
+				put_page(page);
+		}
 		return RESUME_GUEST;
 	}
 	pte = *ptep;
@@ -870,9 +874,14 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 		*levelp = level;
 
 	if (page) {
-		if (!ret && (pte_val(pte) & _PAGE_WRITE))
-			set_page_dirty_lock(page);
-		put_page(page);
+		bool dirty = !ret && (pte_val(pte) & _PAGE_WRITE);
+		if (upgrade_write)
+			put_user_pages_dirty_lock(&page, 1, dirty);
+		else {
+			if (dirty)
+				set_page_dirty_lock(page);
+			put_page(page);
+		}
 	}
 
 	/* Increment number of large pages if we (successfully) inserted one */
diff --git a/arch/powerpc/kvm/e500_mmu.c b/arch/powerpc/kvm/e500_mmu.c
index 2d910b87e441..67bb8d59d4b1 100644
--- a/arch/powerpc/kvm/e500_mmu.c
+++ b/arch/powerpc/kvm/e500_mmu.c
@@ -850,8 +850,7 @@ int kvm_vcpu_ioctl_config_tlb(struct kvm_vcpu *vcpu,
  free_privs_first:
 	kfree(privs[0]);
  put_pages:
-	for (i = 0; i < num_pages; i++)
-		put_page(pages[i]);
+	put_user_pages(pages, num_pages);
  free_pages:
 	kfree(pages);
 	return ret;
diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
index b056cae3388b..e126193ba295 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -170,9 +170,8 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
 	return 0;
 
 free_exit:
-	/* free the reference taken */
-	for (i = 0; i < pinned; i++)
-		put_page(mem->hpages[i]);
+	/* free the references taken */
+	put_user_pages(mem->hpages, pinned);
 
 	vfree(mem->hpas);
 	kfree(mem);
@@ -203,6 +202,7 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
 {
 	long i;
 	struct page *page = NULL;
+	bool dirty = false;
 
 	if (!mem->hpas)
 		return;
@@ -215,10 +215,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
 		if (!page)
 			continue;
 
-		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
-			SetPageDirty(page);
+		dirty = mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY;
 
-		put_page(page);
+		put_user_pages_dirty_lock(&page, 1, dirty);
 		mem->hpas[i] = 0;
 	}
 }
-- 
2.22.0

Re: [PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[Michael Ellerman]

Hi John,

john.hubbard@gmail.com writes:
> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
> index b056cae3388b..e126193ba295 100644
> --- a/arch/powerpc/mm/book3s64/iommu_api.c
> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
> @@ -203,6 +202,7 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>  {
>  	long i;
>  	struct page *page = NULL;
> +	bool dirty = false;

I don't think you need that initialisation do you?

>  	if (!mem->hpas)
>  		return;
> @@ -215,10 +215,9 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>  		if (!page)
>  			continue;
>  
> -		if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
> -			SetPageDirty(page);
> +		dirty = mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY;
> -		put_page(page);
> +		put_user_pages_dirty_lock(&page, 1, dirty);
>  		mem->hpas[i] = 0;
>  	}
>  }

cheers

Re: [PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[John Hubbard]

On 8/7/19 10:42 PM, Michael Ellerman wrote:
> Hi John,
> 
> john.hubbard@gmail.com writes:
>> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
>> index b056cae3388b..e126193ba295 100644
>> --- a/arch/powerpc/mm/book3s64/iommu_api.c
>> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
>> @@ -203,6 +202,7 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>>  {
>>  	long i;
>>  	struct page *page = NULL;
>> +	bool dirty = false;
> 
> I don't think you need that initialisation do you?
> 

Nope, it can go. Fixed locally, thanks.

Did you get a chance to look at enough of the other bits to feel comfortable 
with the patch, overall?

thanks,
-- 
John Hubbard
NVIDIA

Re: [PATCH v3 38/41] powerpc: convert put_page() to put_user_page*()

[Michael Ellerman]

John Hubbard <jhubbard@nvidia.com> writes:
> On 8/7/19 10:42 PM, Michael Ellerman wrote:
>> Hi John,
>> 
>> john.hubbard@gmail.com writes:
>>> diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
>>> index b056cae3388b..e126193ba295 100644
>>> --- a/arch/powerpc/mm/book3s64/iommu_api.c
>>> +++ b/arch/powerpc/mm/book3s64/iommu_api.c
>>> @@ -203,6 +202,7 @@ static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>>>  {
>>>  	long i;
>>>  	struct page *page = NULL;
>>> +	bool dirty = false;
>> 
>> I don't think you need that initialisation do you?
>> 
>
> Nope, it can go. Fixed locally, thanks.

Thanks.

> Did you get a chance to look at enough of the other bits to feel comfortable 
> with the patch, overall?

Mostly :) It's not really my area, but all the conversions looked
correct to me as best as I could tell.

So I'm fine for it to go in as part of the series:

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers