[PATCH v2 1/4] mm/memory: convert do_page_mkwrite() to use folios

[PATCH v2 1/4] mm/memory: convert do_page_mkwrite() to use folios

[Sidhartha Kumar]

Saves one implicit call to compound_head();

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---

v2:
	change folio_mapping() to folio->mapping
	
 mm/memory.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 21fab27272092..e73245b791a7a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2932,7 +2932,7 @@ static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
 static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 {
 	vm_fault_t ret;
-	struct page *page = vmf->page;
+	struct folio *folio = page_folio(vmf->page);
 	unsigned int old_flags = vmf->flags;
 
 	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
@@ -2947,14 +2947,14 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
 		return ret;
 	if (unlikely(!(ret & VM_FAULT_LOCKED))) {
-		lock_page(page);
-		if (!page->mapping) {
-			unlock_page(page);
+		folio_lock(folio);
+		if (!folio->mapping) {
+			folio_unlock(folio);
 			return 0; /* retry */
 		}
 		ret |= VM_FAULT_LOCKED;
 	} else
-		VM_BUG_ON_PAGE(!PageLocked(page), page);
+		VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	return ret;
 }
 
-- 
2.41.0

[PATCH v2 2/4] mm/memory: convert wp_page_shared() to use folios

[Sidhartha Kumar]

Saves five implicit calls to compound_head().

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---
	v2:
		- change function definition to pass in a folio

 mm/memory.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index e73245b791a7a..fba33fb55a010 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3281,13 +3281,13 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
 	return 0;
 }
 
-static vm_fault_t wp_page_shared(struct vm_fault *vmf)
+static vm_fault_t wp_page_shared(struct vm_fault *vmf, struct folio *folio)
 	__releases(vmf->ptl)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret = 0;
 
-	get_page(vmf->page);
+	folio_get(folio);
 
 	if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
 		vm_fault_t tmp;
@@ -3296,21 +3296,21 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf)
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp || (tmp &
 				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
-			put_page(vmf->page);
+			folio_put(folio);
 			return tmp;
 		}
 		tmp = finish_mkwrite_fault(vmf);
 		if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
-			unlock_page(vmf->page);
-			put_page(vmf->page);
+			folio_unlock(folio);
+			folio_put(folio);
 			return tmp;
 		}
 	} else {
 		wp_page_reuse(vmf);
-		lock_page(vmf->page);
+		folio_lock(folio);
 	}
 	ret |= fault_dirty_shared_page(vmf);
-	put_page(vmf->page);
+	folio_put(folio);
 
 	return ret;
 }
@@ -3375,7 +3375,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
 		 */
 		if (!vmf->page)
 			return wp_pfn_shared(vmf);
-		return wp_page_shared(vmf);
+		return wp_page_shared(vmf, page_folio(vmf->page));
 	}
 
 	if (vmf->page)
-- 
2.41.0

Re: [PATCH v2 2/4] mm/memory: convert wp_page_shared() to use folios

[Matthew Wilcox]

On Wed, Jul 05, 2023 at 12:43:33PM -0700, Sidhartha Kumar wrote:
> @@ -3375,7 +3375,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
>  		 */
>  		if (!vmf->page)
>  			return wp_pfn_shared(vmf);
> -		return wp_page_shared(vmf);
> +		return wp_page_shared(vmf, page_folio(vmf->page));
>  	}
>  
>  	if (vmf->page)

I was actually hoping you'd move:

        if (vmf->page)
                folio = page_folio(vmf->page);

up to immediately after the call to vm_normal_page(), and avoid even
this call to page_folio().

[PATCH v2 3/4] mm/memory: convert do_shared_fault() to folios

[Sidhartha Kumar]

Saves three implicit calls to compound_head().

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---

v2:
	 - move folio initialization after __do_fault()

 mm/memory.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index fba33fb55a010..ce7826d3f6200 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4593,21 +4593,24 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret, tmp;
+	struct folio *folio;
 
 	ret = __do_fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
 		return ret;
 
+	folio = page_folio(vmf->page);
+
 	/*
 	 * Check if the backing address space wants to know that the page is
 	 * about to become writable
 	 */
 	if (vma->vm_ops->page_mkwrite) {
-		unlock_page(vmf->page);
+		folio_unlock(folio);
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp ||
 				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
-			put_page(vmf->page);
+			folio_put(folio);
 			return tmp;
 		}
 	}
@@ -4615,8 +4618,8 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
 	ret |= finish_fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
 					VM_FAULT_RETRY))) {
-		unlock_page(vmf->page);
-		put_page(vmf->page);
+		folio_unlock(folio);
+		folio_put(folio);
 		return ret;
 	}
 
-- 
2.41.0

Re: [PATCH v2 3/4] mm/memory: convert do_shared_fault() to folios

[Matthew Wilcox]

On Wed, Jul 05, 2023 at 12:43:34PM -0700, Sidhartha Kumar wrote:
>  	/*
>  	 * Check if the backing address space wants to know that the page is
>  	 * about to become writable
>  	 */
>  	if (vma->vm_ops->page_mkwrite) {
> -		unlock_page(vmf->page);
> +		folio_unlock(folio);
>  		tmp = do_page_mkwrite(vmf);
>  		if (unlikely(!tmp ||
>  				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
> -			put_page(vmf->page);
> +			folio_put(folio);

This is _probably_ OK.  However, do_page_mkwrite() calls
vm_ops->page_mkwrite(), and I think it's theoretically possible for the
driver to replace vmf->page with a different one.  The chance of them
actually doing that is pretty low (particularly if they return error or
nopage!), but I'm going to flag it just in case it comes up.

Also, should we pass a folio to do_page_mkwrite() instead of having it
extract the folio from vmf->page?

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Re: [PATCH v2 3/4] mm/memory: convert do_shared_fault() to folios

[Sidhartha Kumar]

On 7/5/23 1:13 PM, Matthew Wilcox wrote:
> On Wed, Jul 05, 2023 at 12:43:34PM -0700, Sidhartha Kumar wrote:
>>   	/*
>>   	 * Check if the backing address space wants to know that the page is
>>   	 * about to become writable
>>   	 */
>>   	if (vma->vm_ops->page_mkwrite) {
>> -		unlock_page(vmf->page);
>> +		folio_unlock(folio);
>>   		tmp = do_page_mkwrite(vmf);
>>   		if (unlikely(!tmp ||
>>   				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
>> -			put_page(vmf->page);
>> +			folio_put(folio);
> 
> This is _probably_ OK.  However, do_page_mkwrite() calls
> vm_ops->page_mkwrite(), and I think it's theoretically possible for the
> driver to replace vmf->page with a different one.  The chance of them
> actually doing that is pretty low (particularly if they return error or
> nopage!), but I'm going to flag it just in case it comes up.
> 
> Also, should we pass a folio to do_page_mkwrite() instead of having it
> extract the folio from vmf->page?

I can take a look at doing this in a follow-up patch.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Did you mean for this to be reviewed-by?

Thanks,
Sidhartha Kumar

Re: [PATCH v2 3/4] mm/memory: convert do_shared_fault() to folios

[Matthew Wilcox]

On Wed, Jul 05, 2023 at 01:16:25PM -0700, Sidhartha Kumar wrote:
> On 7/5/23 1:13 PM, Matthew Wilcox wrote:
> > On Wed, Jul 05, 2023 at 12:43:34PM -0700, Sidhartha Kumar wrote:
> > >   	/*
> > >   	 * Check if the backing address space wants to know that the page is
> > >   	 * about to become writable
> > >   	 */
> > >   	if (vma->vm_ops->page_mkwrite) {
> > > -		unlock_page(vmf->page);
> > > +		folio_unlock(folio);
> > >   		tmp = do_page_mkwrite(vmf);
> > >   		if (unlikely(!tmp ||
> > >   				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
> > > -			put_page(vmf->page);
> > > +			folio_put(folio);
> > 
> > This is _probably_ OK.  However, do_page_mkwrite() calls
> > vm_ops->page_mkwrite(), and I think it's theoretically possible for the
> > driver to replace vmf->page with a different one.  The chance of them
> > actually doing that is pretty low (particularly if they return error or
> > nopage!), but I'm going to flag it just in case it comes up.
> > 
> > Also, should we pass a folio to do_page_mkwrite() instead of having it
> > extract the folio from vmf->page?
> 
> I can take a look at doing this in a follow-up patch.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> Did you mean for this to be reviewed-by?

Uh, yes.  Maybe I need to get more rest ...

[PATCH v2 4/4] mm/memory: convert do_read_fault() to use folios

[Sidhartha Kumar]

Saves one implicit call to compound_head()

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---
v2
	 - move folio initialization after __do_fault()

 mm/memory.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index ce7826d3f6200..e40a03e488ca2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4527,6 +4527,7 @@ static inline bool should_fault_around(struct vm_fault *vmf)
 static vm_fault_t do_read_fault(struct vm_fault *vmf)
 {
 	vm_fault_t ret = 0;
+	struct folio *folio;
 
 	/*
 	 * Let's call ->map_pages() first and use ->fault() as fallback
@@ -4543,10 +4544,12 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
 		return ret;
 
+	folio = page_folio(vmf->page);
+
 	ret |= finish_fault(vmf);
-	unlock_page(vmf->page);
+	folio_unlock(folio);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
-		put_page(vmf->page);
+		folio_put(folio);
 	return ret;
 }
 
-- 
2.41.0

Re: [PATCH v2 4/4] mm/memory: convert do_read_fault() to use folios

[Matthew Wilcox]

On Wed, Jul 05, 2023 at 12:43:35PM -0700, Sidhartha Kumar wrote:
> Saves one implicit call to compound_head()
> 
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

> @@ -4543,10 +4544,12 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
>  	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
>  		return ret;
>  
> +	folio = page_folio(vmf->page);

Why not move this down to after the call to finish_fault()?  The
compiler should be able to do a better job with that; it may have to
spill it to the stack to preserve it over the function call.

>  	ret |= finish_fault(vmf);
> -	unlock_page(vmf->page);
> +	folio_unlock(folio);
>  	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
> -		put_page(vmf->page);
> +		folio_put(folio);
>  	return ret;

Re: [PATCH v2 4/4] mm/memory: convert do_read_fault() to use folios

[Sidhartha Kumar]

On 7/5/23 1:19 PM, Matthew Wilcox wrote:
> On Wed, Jul 05, 2023 at 12:43:35PM -0700, Sidhartha Kumar wrote:
>> Saves one implicit call to compound_head()
>>
>> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
> 
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
>> @@ -4543,10 +4544,12 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
>>   	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
>>   		return ret;
>>   
>> +	folio = page_folio(vmf->page);
> 
> Why not move this down to after the call to finish_fault()?  The
> compiler should be able to do a better job with that; it may have to
> spill it to the stack to preserve it over the function call.
> 

I just noticed that the page inside the vmf was being used in 
finish_fault() so it would stable enough to do the folio conversion 
before. I can move it after for compiler reasons.

>>   	ret |= finish_fault(vmf);
>> -	unlock_page(vmf->page);
>> +	folio_unlock(folio);
>>   	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
>> -		put_page(vmf->page);
>> +		folio_put(folio);
>>   	return ret;
> 
> 

Re: [PATCH v2 1/4] mm/memory: convert do_page_mkwrite() to use folios

[Matthew Wilcox]

On Wed, Jul 05, 2023 at 12:43:32PM -0700, Sidhartha Kumar wrote:
> Saves one implicit call to compound_head();
> 
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>