[PATCH 0/7] Cleanup free_pages() misuse

[PATCH 0/7] Cleanup free_pages() misuse

[Vishal Moola (Oracle)]

free_pages() is supposed to be called when we only have a virtual address.
__free_pages() is supposed to be called when we have a page.

There are a number of callers that use page_address() to get a page's
virtual address then call free_pages() on it when they should just call
__free_pages() directly.

Add kernel-docs for free_pages() to help callers better understand which
function they should be calling, and replace the obvious cases of
misuse.

-----------------
Based on mm-new. I intend to have all of these taken through the mm tree.

I've split the patches into separate subsystems to make it easier to
resolve conflicts, but there aren't any functional changes.

Vishal Moola (Oracle) (7):
  mm/page_alloc: Add kernel-docs for free_pages()
  aoe: Stop calling page_address() in free_page()
  x86: Stop calling page_address() in free_pages()
  riscv: Stop calling page_address() in free_pages()
  powerpc: Stop calling page_address() in free_pages()
  arm64: Stop calling page_address() in free_pages()
  virtio_balloon: Stop calling page_address() in free_pages()

 arch/arm64/mm/mmu.c                      | 2 +-
 arch/powerpc/mm/book3s64/radix_pgtable.c | 2 +-
 arch/riscv/mm/init.c                     | 4 ++--
 arch/x86/mm/init_64.c                    | 2 +-
 arch/x86/platform/efi/memmap.c           | 2 +-
 drivers/block/aoe/aoecmd.c               | 2 +-
 drivers/virtio/virtio_balloon.c          | 3 +--
 mm/page_alloc.c                          | 9 +++++++++
 8 files changed, 17 insertions(+), 9 deletions(-)

-- 
2.51.0

[PATCH 1/7] mm/page_alloc: Add kernel-docs for free_pages()

[Vishal Moola (Oracle)]

Add kernel-docs to free_pages(). This will help callers understand when
to use it instead of __free_pages().

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 mm/page_alloc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index baead29b3e67..6ee8f450c078 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5270,6 +5270,15 @@ void free_pages_nolock(struct page *page, unsigned int order)
 	___free_pages(page, order, FPI_TRYLOCK);
 }
 
+/**
+ * free_pages - Free pages allocated with alloc_pages().
+ * @addr: The virtual address tied to a page returned from alloc_pages().
+ * @order: The order of the allocation.
+ *
+ * This function behaves the same as __free_pages(). Use this function
+ * to free pages when you only have a valid virtual address. If you have
+ * the page, call __free_pages() instead.
+ */
 void free_pages(unsigned long addr, unsigned int order)
 {
 	if (addr != 0) {
-- 
2.51.0

Re: [PATCH 1/7] mm/page_alloc: Add kernel-docs for free_pages()

[Matthew Wilcox]

On Tue, Aug 26, 2025 at 12:32:52PM -0700, Vishal Moola (Oracle) wrote:
> +/**
> + * free_pages - Free pages allocated with alloc_pages().

I might reference get_free_pages() here instead of alloc_pages().
We used to have a wonderful document that explained that there was one
allocator with two namespaces to access it; alloc_pages()/__free_pages()
and get_free_pages()/free_pages().  I don't know what happened to it.

Other than that,

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

[PATCH 2/7] aoe: Stop calling page_address() in free_page()

[Vishal Moola (Oracle)]

free_page() should be used when we only have a virtual address. We
should call __free_page() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 drivers/block/aoe/aoecmd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 6298f8e271e3..a9affb7c264d 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -1761,6 +1761,6 @@ aoecmd_exit(void)
 	kfree(kts);
 	kfree(ktiowq);
 
-	free_page((unsigned long) page_address(empty_page));
+	__free_page(empty_page);
 	empty_page = NULL;
 }
-- 
2.51.0

Re: [PATCH 2/7] aoe: Stop calling page_address() in free_page()

[Matthew Wilcox]

On Tue, Aug 26, 2025 at 12:32:53PM -0700, Vishal Moola (Oracle) wrote:
> free_page() should be used when we only have a virtual address. We
> should call __free_page() directly on our page instead.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>

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

Probably should have run ./scripts/get_maintainer.pl drivers/block/aoe/aoecmd.c
Adding ccs.

>  drivers/block/aoe/aoecmd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
> index 6298f8e271e3..a9affb7c264d 100644
> --- a/drivers/block/aoe/aoecmd.c
> +++ b/drivers/block/aoe/aoecmd.c
> @@ -1761,6 +1761,6 @@ aoecmd_exit(void)
>  	kfree(kts);
>  	kfree(ktiowq);
>  
> -	free_page((unsigned long) page_address(empty_page));
> +	__free_page(empty_page);
>  	empty_page = NULL;
>  }
> -- 
> 2.51.0
> 
> 

Re: [PATCH 2/7] aoe: Stop calling page_address() in free_page()

[Vishal Moola (Oracle)]

On Tue, Aug 26, 2025 at 08:41:03PM +0100, Matthew Wilcox wrote:
> On Tue, Aug 26, 2025 at 12:32:53PM -0700, Vishal Moola (Oracle) wrote:
> > free_page() should be used when we only have a virtual address. We
> > should call __free_page() directly on our page instead.
> > 
> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> 
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> Probably should have run ./scripts/get_maintainer.pl drivers/block/aoe/aoecmd.c
> Adding ccs.

Ah I thought I did that... seems I messed up some formatting and none of
the ccs got added :/. I'll send out a v2 later today with all the ccs
added.

> >  drivers/block/aoe/aoecmd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
> > index 6298f8e271e3..a9affb7c264d 100644
> > --- a/drivers/block/aoe/aoecmd.c
> > +++ b/drivers/block/aoe/aoecmd.c
> > @@ -1761,6 +1761,6 @@ aoecmd_exit(void)
> >  	kfree(kts);
> >  	kfree(ktiowq);
> >  
> > -	free_page((unsigned long) page_address(empty_page));
> > +	__free_page(empty_page);
> >  	empty_page = NULL;
> >  }
> > -- 
> > 2.51.0
> > 
> > 

[PATCH 3/7] x86: Stop calling page_address() in free_pages()

[Vishal Moola (Oracle)]

free_pages() should be used when we only have a virtual address. We
should call __free_pages() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/x86/mm/init_64.c          | 2 +-
 arch/x86/platform/efi/memmap.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index b9426fce5f3e..0e4270e20fad 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1031,7 +1031,7 @@ static void __meminit free_pagetable(struct page *page, int order)
 		free_reserved_pages(page, nr_pages);
 #endif
 	} else {
-		free_pages((unsigned long)page_address(page), order);
+		__free_pages(page, order);
 	}
 }
 
diff --git a/arch/x86/platform/efi/memmap.c b/arch/x86/platform/efi/memmap.c
index 061b8ecc71a1..023697c88910 100644
--- a/arch/x86/platform/efi/memmap.c
+++ b/arch/x86/platform/efi/memmap.c
@@ -42,7 +42,7 @@ void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
 		struct page *p = pfn_to_page(PHYS_PFN(phys));
 		unsigned int order = get_order(size);
 
-		free_pages((unsigned long) page_address(p), order);
+		__free_pages(p, order);
 	}
 }
 
-- 
2.51.0

[PATCH 4/7] riscv: Stop calling page_address() in free_pages()

[Vishal Moola (Oracle)]

free_pages() should be used when we only have a virtual address. We
should call __free_pages() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/riscv/mm/init.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 15683ae13fa5..1056c11d3251 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1624,7 +1624,7 @@ static void __meminit free_pud_table(pud_t *pud_start, p4d_t *p4d)
 	if (PageReserved(page))
 		free_reserved_page(page);
 	else
-		free_pages((unsigned long)page_address(page), 0);
+		__free_pages(page, 0);
 	p4d_clear(p4d);
 }
 
@@ -1646,7 +1646,7 @@ static void __meminit free_vmemmap_storage(struct page *page, size_t size,
 		return;
 	}
 
-	free_pages((unsigned long)page_address(page), order);
+	__free_pages(page, order);
 }
 
 static void __meminit remove_pte_mapping(pte_t *pte_base, unsigned long addr, unsigned long end,
-- 
2.51.0

[PATCH 5/7] powerpc: Stop calling page_address() in free_pages()

[Vishal Moola (Oracle)]

free_pages() should be used when we only have a virtual address. We
should call __free_pages() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/powerpc/mm/book3s64/radix_pgtable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index be523e5fe9c5..73977dbabcf2 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -780,7 +780,7 @@ static void __meminit free_vmemmap_pages(struct page *page,
 		while (nr_pages--)
 			free_reserved_page(page++);
 	} else
-		free_pages((unsigned long)page_address(page), order);
+		__free_pages(page, order);
 }
 
 static void __meminit remove_pte_table(pte_t *pte_start, unsigned long addr,
-- 
2.51.0

[PATCH 6/7] arm64: Stop calling page_address() in free_pages()

[Vishal Moola (Oracle)]

free_pages() should be used when we only have a virtual address. We
should call __free_pages() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/arm64/mm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 34e5d78af076..e14a75d0dbd3 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -843,7 +843,7 @@ static void free_hotplug_page_range(struct page *page, size_t size,
 		vmem_altmap_free(altmap, size >> PAGE_SHIFT);
 	} else {
 		WARN_ON(PageReserved(page));
-		free_pages((unsigned long)page_address(page), get_order(size));
+		__free_pages(page, get_order(size));
 	}
 }
 
-- 
2.51.0

[PATCH 7/7] virtio_balloon: Stop calling page_address() in free_pages()

[Vishal Moola (Oracle)]

free_pages() should be used when we only have a virtual address. We
should call __free_pages() directly on our page instead.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 drivers/virtio/virtio_balloon.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index eae65136cdfb..d4e6865ce355 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -488,8 +488,7 @@ static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
 		page = balloon_page_pop(&vb->free_page_list);
 		if (!page)
 			break;
-		free_pages((unsigned long)page_address(page),
-			   VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
 	}
 	vb->num_free_page_blocks -= num_returned;
 	spin_unlock_irq(&vb->free_page_list_lock);
-- 
2.51.0