[PATCH 0/3] Remove unmap_and_put_page()

[PATCH 0/3] Remove unmap_and_put_page()

[Vishal Moola (Oracle)]

This patchset uses folios in both the callers of
unmap_and_put_page(), saving a couple calls to compound_head() wrappers.

----

The initial rfc[1] attempted to provide large folio support for the
caller functions. Trying to do this without the relevant "struct page"
is excessive and unnecessary right now.

[1] https://lore.kernel.org/linux-mm/20250625174841.1094510-1-vishal.moola@gmail.com/

Vishal Moola (Oracle) (3):
  mm/memory.c: Use folios in __copy_remote_vm_str()
  mm/memory.c: Use folios in __access_remote_vm()
  mm: Remove unmap_and_put_page()

 include/linux/highmem.h |  6 ------
 mm/memory.c             | 16 ++++++++++------
 2 files changed, 10 insertions(+), 12 deletions(-)

-- 
2.50.0

[PATCH 1/3] mm/memory.c: Use folios in __copy_remote_vm_str()

[Vishal Moola (Oracle)]

Use kmap_local_folio() instead of kmap_local_page().
Replaces 2 calls to compound_head() from unmap_and_put_page() with one.

This prepares us for the removal of unmap_and_put_page().

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 mm/memory.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 1174f3001307..d63f0d5abcc9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6815,6 +6815,7 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr,
 	while (len) {
 		int bytes, offset, retval;
 		void *maddr;
+		struct folio *folio;
 		struct page *page;
 		struct vm_area_struct *vma = NULL;
 
@@ -6830,17 +6831,18 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr,
 			goto out;
 		}
 
+		folio = page_folio(page);
 		bytes = len;
 		offset = addr & (PAGE_SIZE - 1);
 		if (bytes > PAGE_SIZE - offset)
 			bytes = PAGE_SIZE - offset;
 
-		maddr = kmap_local_page(page);
+		maddr = kmap_local_folio(folio, folio_page_idx(folio, page) * PAGE_SIZE);
 		retval = strscpy(buf, maddr + offset, bytes);
 		if (retval >= 0) {
 			/* Found the end of the string */
 			buf += retval;
-			unmap_and_put_page(page, maddr);
+			folio_release_kmap(folio, maddr);
 			break;
 		}
 
@@ -6858,7 +6860,7 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr,
 		}
 		len -= bytes;
 
-		unmap_and_put_page(page, maddr);
+		folio_release_kmap(folio, maddr);
 	}
 
 out:
-- 
2.50.0

[PATCH 2/3] mm/memory.c: Use folios in __access_remote_vm()

[Vishal Moola (Oracle)]

Use kmap_local_folio() instead of kmap_local_page().
Replaces 2 calls to compound_head() with one.

This prepares us for the removal of unmap_and_put_page().

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 mm/memory.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d63f0d5abcc9..3dd6c57e6511 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6691,6 +6691,7 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
 	while (len) {
 		int bytes, offset;
 		void *maddr;
+		struct folio *folio;
 		struct vm_area_struct *vma = NULL;
 		struct page *page = get_user_page_vma_remote(mm, addr,
 							     gup_flags, &vma);
@@ -6722,21 +6723,22 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
 			if (bytes <= 0)
 				break;
 		} else {
+			folio = page_folio(page);
 			bytes = len;
 			offset = addr & (PAGE_SIZE-1);
 			if (bytes > PAGE_SIZE-offset)
 				bytes = PAGE_SIZE-offset;
 
-			maddr = kmap_local_page(page);
+			maddr = kmap_local_folio(folio, folio_page_idx(folio, page) * PAGE_SIZE);
 			if (write) {
 				copy_to_user_page(vma, page, addr,
 						  maddr + offset, buf, bytes);
-				set_page_dirty_lock(page);
+				folio_mark_dirty_lock(folio);
 			} else {
 				copy_from_user_page(vma, page, addr,
 						    buf, maddr + offset, bytes);
 			}
-			unmap_and_put_page(page, maddr);
+			folio_release_kmap(folio, maddr);
 		}
 		len -= bytes;
 		buf += bytes;
-- 
2.50.0

[PATCH 3/3] mm: Remove unmap_and_put_page()

[Vishal Moola (Oracle)]

There are no callers of unmap_and_put_page() left. Remove it.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 include/linux/highmem.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index a30526cc53a7..6234f316468c 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -682,10 +682,4 @@ static inline void folio_release_kmap(struct folio *folio, void *addr)
 	kunmap_local(addr);
 	folio_put(folio);
 }
-
-static inline void unmap_and_put_page(struct page *page, void *addr)
-{
-	folio_release_kmap(page_folio(page), addr);
-}
-
 #endif /* _LINUX_HIGHMEM_H */
-- 
2.50.0

Re: [PATCH 1/3] mm/memory.c: Use folios in __copy_remote_vm_str()

[David Hildenbrand]

On 09.07.25 21:40, Vishal Moola (Oracle) wrote:
> Use kmap_local_folio() instead of kmap_local_page().
> Replaces 2 calls to compound_head() from unmap_and_put_page() with one.
> 
> This prepares us for the removal of unmap_and_put_page().
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> ---
>   mm/memory.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 1174f3001307..d63f0d5abcc9 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -6815,6 +6815,7 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr,
>   	while (len) {
>   		int bytes, offset, retval;
>   		void *maddr;
> +		struct folio *folio;
>   		struct page *page;
>   		struct vm_area_struct *vma = NULL;
>   
> @@ -6830,17 +6831,18 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr,
>   			goto out;
>   		}
>   
> +		folio = page_folio(page);
>   		bytes = len;
>   		offset = addr & (PAGE_SIZE - 1);
>   		if (bytes > PAGE_SIZE - offset)
>   			bytes = PAGE_SIZE - offset;
>   
> -		maddr = kmap_local_page(page);
> +		maddr = kmap_local_folio(folio, folio_page_idx(folio, page) * PAGE_SIZE);

It's weird to go page -> folio -> page ... but maybe that's just the way 
it's supposed to work here ...

:)

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 2/3] mm/memory.c: Use folios in __access_remote_vm()

[David Hildenbrand]

On 09.07.25 21:40, Vishal Moola (Oracle) wrote:
> Use kmap_local_folio() instead of kmap_local_page().
> Replaces 2 calls to compound_head() with one.
> 
> This prepares us for the removal of unmap_and_put_page().
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> ---
>   mm/memory.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index d63f0d5abcc9..3dd6c57e6511 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -6691,6 +6691,7 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
>   	while (len) {
>   		int bytes, offset;
>   		void *maddr;
> +		struct folio *folio;
>   		struct vm_area_struct *vma = NULL;
>   		struct page *page = get_user_page_vma_remote(mm, addr,
>   							     gup_flags, &vma);
> @@ -6722,21 +6723,22 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr,
>   			if (bytes <= 0)
>   				break;
>   		} else {
> +			folio = page_folio(page);
>   			bytes = len;
>   			offset = addr & (PAGE_SIZE-1);
>   			if (bytes > PAGE_SIZE-offset)
>   				bytes = PAGE_SIZE-offset;
>   
> -			maddr = kmap_local_page(page);
> +			maddr = kmap_local_folio(folio, folio_page_idx(folio, page) * PAGE_SIZE);
>   			if (write) {
>   				copy_to_user_page(vma, page, addr,
>   						  maddr + offset, buf, bytes);
> -				set_page_dirty_lock(page);
> +				folio_mark_dirty_lock(folio);
>   			} else {
>   				copy_from_user_page(vma, page, addr,
>   						    buf, maddr + offset, bytes);
>   			}
> -			unmap_and_put_page(page, maddr);
> +			folio_release_kmap(folio, maddr);

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 3/3] mm: Remove unmap_and_put_page()

[David Hildenbrand]

On 09.07.25 21:40, Vishal Moola (Oracle) wrote:
> There are no callers of unmap_and_put_page() left. Remove it.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> ---
>   include/linux/highmem.h | 6 ------
>   1 file changed, 6 deletions(-)
> 
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index a30526cc53a7..6234f316468c 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -682,10 +682,4 @@ static inline void folio_release_kmap(struct folio *folio, void *addr)
>   	kunmap_local(addr);
>   	folio_put(folio);
>   }
> -
> -static inline void unmap_and_put_page(struct page *page, void *addr)
> -{
> -	folio_release_kmap(page_folio(page), addr);
> -}
> -
>   #endif /* _LINUX_HIGHMEM_H */

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb