Commit af385388 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/memory: factor out common code from vm_normal_page_*() 

Let's reduce the code duplication and factor out the non-pte/pmd related
magic into __vm_normal_page().

To keep it simpler, check the pfn against both zero folios, which
shouldn't really make a difference.

It's a good question if we can even hit the !CONFIG_ARCH_HAS_PTE_SPECIAL
scenario in the PMD case in practice: but doesn't really matter, as it's
now all unified in vm_normal_page_pfn().

Add kerneldoc for all involved functions.

Note that, as a side product, we now:
* Support the find_special_page special thingy also for PMD
* Don't check for is_huge_zero_pfn() anymore if we have
  CONFIG_ARCH_HAS_PTE_SPECIAL and the PMD is not special. The
  VM_WARN_ON_ONCE would catch any abuse

No functional change intended.

Link: https://lkml.kernel.org/r/20250811112631.759341-10-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Juegren Gross <jgross@suse.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent ec63a440

mm/memory.c

+109 −77
Original line number Diff line number Diff line
@@ -614,8 +614,14 @@ static void print_bad_page_map(struct vm_area_struct *vma, 
#define print_bad_pte(vma, addr, pte, page) \

	print_bad_page_map(vma, addr, pte_val(pte), page, PGTABLE_LEVEL_PTE)



/*

 * vm_normal_page -- This function gets the "struct page" associated with a pte.

/**

 * __vm_normal_page() - Get the "struct page" associated with a page table entry.

 * @vma: The VMA mapping the page table entry.

 * @addr: The address where the page table entry is mapped.

 * @pfn: The PFN stored in the page table entry.

 * @special: Whether the page table entry is marked "special".

 * @level: The page table level for error reporting purposes only.

 * @entry: The page table entry value for error reporting purposes only.

 *

 * "Special" mappings do not wish to be associated with a "struct page" (either

 * it doesn't exist, or it exists but they don't want to touch it). In this
@@ -628,10 +634,10 @@ static void print_bad_page_map(struct vm_area_struct *vma, 
 * Selected page table walkers (such as GUP) can still identify mappings of the

 * shared zero folios and work with the underlying "struct page".

 *

 * There are 2 broad cases. Firstly, an architecture may define a pte_special()

 * pte bit, in which case this function is trivial. Secondly, an architecture

 * may not have a spare pte bit, which requires a more complicated scheme,

 * described below.

 * There are 2 broad cases. Firstly, an architecture may define a "special"

 * page table entry bit, such as pte_special(), in which case this function is

 * trivial. Secondly, an architecture may not have a spare page table

 * entry bit, which requires a more complicated scheme, described below.

 *

 * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a

 * special mapping (even if there are underlying and valid "struct pages").
@@ -664,38 +670,39 @@ static void print_bad_page_map(struct vm_area_struct *vma, 
 * don't have to follow the strict linearity rule of PFNMAP mappings in

 * order to support COWable mappings.

 *

 * Return: Returns the "struct page" if this is a "normal" mapping. Returns

 *	   NULL if this is a "special" mapping.

 */

struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,

			    pte_t pte)

static inline struct page *__vm_normal_page(struct vm_area_struct *vma,

		unsigned long addr, unsigned long pfn, bool special,

		unsigned long long entry, enum pgtable_level level)

{

	unsigned long pfn = pte_pfn(pte);



	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {

		if (likely(!pte_special(pte)))

			goto check_pfn;

		if (unlikely(special)) {

			if (vma->vm_ops && vma->vm_ops->find_special_page)

				return vma->vm_ops->find_special_page(vma, addr);

			if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))

				return NULL;

		if (is_zero_pfn(pfn))

			if (is_zero_pfn(pfn) || is_huge_zero_pfn(pfn))

				return NULL;



		print_bad_pte(vma, addr, pte, NULL);

			print_bad_page_map(vma, addr, entry, NULL, level);

			return NULL;

		}



	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */



		/*

		 * With CONFIG_ARCH_HAS_PTE_SPECIAL, any special page table

		 * mappings (incl. shared zero folios) are marked accordingly.

		 */

	} else {

		if (unlikely(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))) {

			if (vma->vm_flags & VM_MIXEDMAP) {

				/* If it has a "struct page", it's "normal". */

				if (!pfn_valid(pfn))

					return NULL;

			if (is_zero_pfn(pfn))

				return NULL;

			goto out;

			} else {

			unsigned long off;

			off = (addr - vma->vm_start) >> PAGE_SHIFT;

				unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT;



				/* Only CoW'ed anon folios are "normal". */

				if (pfn == vma->vm_pgoff + off)

					return NULL;

				if (!is_cow_mapping(vma->vm_flags))
@@ -703,24 +710,54 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, 
			}

		}



	if (is_zero_pfn(pfn))

		if (is_zero_pfn(pfn) || is_huge_zero_pfn(pfn))

			return NULL;

	}



check_pfn:

	if (unlikely(pfn > highest_memmap_pfn)) {

		print_bad_pte(vma, addr, pte, NULL);

		/* Corrupted page table entry. */

		print_bad_page_map(vma, addr, entry, NULL, level);

		return NULL;

	}



	/*

	 * NOTE! We still have PageReserved() pages in the page tables.

	 * eg. VDSO mappings can cause them to exist.

	 * For example, VDSO mappings can cause them to exist.

	 */

out:

	VM_WARN_ON_ONCE(is_zero_pfn(pfn));

	VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn));

	return pfn_to_page(pfn);

}



/**

 * vm_normal_page() - Get the "struct page" associated with a PTE

 * @vma: The VMA mapping the @pte.

 * @addr: The address where the @pte is mapped.

 * @pte: The PTE.

 *

 * Get the "struct page" associated with a PTE. See __vm_normal_page()

 * for details on "normal" and "special" mappings.

 *

 * Return: Returns the "struct page" if this is a "normal" mapping. Returns

 *	   NULL if this is a "special" mapping.

 */

struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,

			    pte_t pte)

{

	return __vm_normal_page(vma, addr, pte_pfn(pte), pte_special(pte),

				pte_val(pte), PGTABLE_LEVEL_PTE);

}



/**

 * vm_normal_folio() - Get the "struct folio" associated with a PTE

 * @vma: The VMA mapping the @pte.

 * @addr: The address where the @pte is mapped.

 * @pte: The PTE.

 *

 * Get the "struct folio" associated with a PTE. See __vm_normal_page()

 * for details on "normal" and "special" mappings.

 *

 * Return: Returns the "struct folio" if this is a "normal" mapping. Returns

 *	   NULL if this is a "special" mapping.

 */

struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr,

			    pte_t pte)

{
@@ -732,42 +769,37 @@ struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr, 
}



#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES

/**

 * vm_normal_page_pmd() - Get the "struct page" associated with a PMD

 * @vma: The VMA mapping the @pmd.

 * @addr: The address where the @pmd is mapped.

 * @pmd: The PMD.

 *

 * Get the "struct page" associated with a PTE. See __vm_normal_page()

 * for details on "normal" and "special" mappings.

 *

 * Return: Returns the "struct page" if this is a "normal" mapping. Returns

 *	   NULL if this is a "special" mapping.

 */

struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,

				pmd_t pmd)

{

	unsigned long pfn = pmd_pfn(pmd);



	if (unlikely(pmd_special(pmd)))

		return NULL;



	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {

		if (vma->vm_flags & VM_MIXEDMAP) {

			if (!pfn_valid(pfn))

				return NULL;

			goto out;

		} else {

			unsigned long off;

			off = (addr - vma->vm_start) >> PAGE_SHIFT;

			if (pfn == vma->vm_pgoff + off)

				return NULL;

			if (!is_cow_mapping(vma->vm_flags))

				return NULL;

	return __vm_normal_page(vma, addr, pmd_pfn(pmd), pmd_special(pmd),

				pmd_val(pmd), PGTABLE_LEVEL_PMD);

}

	}



	if (is_huge_zero_pfn(pfn))

		return NULL;

	if (unlikely(pfn > highest_memmap_pfn))

		return NULL;



	/*

	 * NOTE! We still have PageReserved() pages in the page tables.

	 * eg. VDSO mappings can cause them to exist.

/**

 * vm_normal_folio_pmd() - Get the "struct folio" associated with a PMD

 * @vma: The VMA mapping the @pmd.

 * @addr: The address where the @pmd is mapped.

 * @pmd: The PMD.

 *

 * Get the "struct folio" associated with a PTE. See __vm_normal_page()

 * for details on "normal" and "special" mappings.

 *

 * Return: Returns the "struct folio" if this is a "normal" mapping. Returns

 *	   NULL if this is a "special" mapping.

 */

out:

	return pfn_to_page(pfn);

}



struct folio *vm_normal_folio_pmd(struct vm_area_struct *vma,

				  unsigned long addr, pmd_t pmd)

{