On Wed, Sep 23, 2026 at 02:28:29PM +0800, Wen Jiang wrote:
> From: "Barry Song (Xiaomi)" <[email protected]>
>
> vmap_pages_range_noflush_walk() (formerly vmap_small_pages_range_noflush())
> provides a clean interface by taking struct page **pages and mapping them
> via direct PTE iteration. This avoids the page table rewalk seen when
> using vmap_range_noflush() for page_shift values other than PAGE_SHIFT.
>
> Extend it to support larger page_shift values, and add PMD- and
> contiguous-PTE mappings as well.
>
> Rename it to vmap_pages_range_noflush_walk() since it now handles
> more than just small pages.
>
> For vmalloc() allocations with VM_ALLOW_HUGE_VMAP, we no longer need to
> iterate over pages one by one via vmap_range_noflush(), which would
> otherwise lead to page table rewalk. The code is now unified with the
> PAGE_SHIFT case by simply calling vmap_pages_range_noflush_walk().
>
> Signed-off-by: Barry Song (Xiaomi) <[email protected]>
> Signed-off-by: Wen Jiang <[email protected]>
> Tested-by: Xueyuan Chen <[email protected]>
> Tested-by: Leo Yan <[email protected]>
> Reviewed-by: Dev Jain <[email protected]>
> ---
> mm/vmalloc.c | 84 +++++++++++++++++++++++++++++++---------------------
> 1 file changed, 50 insertions(+), 34 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index d475e52110e4a..6e0dec73107a7 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -558,8 +558,10 @@ void vunmap_range(unsigned long addr, unsigned long end)
>
> static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
> unsigned long end, pgprot_t prot, struct page **pages, int *nr,
> - pgtbl_mod_mask *mask)
> + pgtbl_mod_mask *mask, unsigned int shift)
> {
> + unsigned long pfn, size;
> + unsigned int steps;
> int err = 0;
> pte_t *pte;
>
> @@ -590,9 +592,10 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned
> long addr,
> break;
> }
>
> - set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
> - (*nr)++;
> - } while (pte++, addr += PAGE_SIZE, addr != end);
> + pfn = page_to_pfn(page);
> + size = vmap_set_ptes(pte, addr, end, pfn, prot, shift);
> + steps = PFN_DOWN(size);
> + } while (pte += steps, *nr += steps, addr += size, addr != end);
>
nr_mapped_pages?
>
> lazy_mmu_mode_disable();
> *mask |= PGTBL_PTE_MODIFIED;
> @@ -602,60 +605,88 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned
> long addr,
>
> static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr,
> unsigned long end, pgprot_t prot, struct page **pages, int *nr,
> - pgtbl_mod_mask *mask)
> + pgtbl_mod_mask *mask, unsigned int shift)
> {
> pmd_t *pmd;
> unsigned long next;
> + int err;
>
> pmd = pmd_alloc_track(&init_mm, pud, addr, mask);
> if (!pmd)
> return -ENOMEM;
> do {
> next = pmd_addr_end(addr, end);
> - if (vmap_pages_pte_range(pmd, addr, next, prot, pages, nr,
> mask))
> - return -ENOMEM;
> +
> + if (shift >= PMD_SHIFT) {
> + struct page *page = pages[*nr];
> + phys_addr_t phys_addr;
> +
> + if (WARN_ON(!page))
> + return -ENOMEM;
> + if (WARN_ON(!pfn_valid(page_to_pfn(page))))
> + return -EINVAL;
> +
> + phys_addr = page_to_phys(page);
> +
> + if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot,
> shift)) {
> + *mask |= PGTBL_PMD_MODIFIED;
> + *nr += 1 << (PMD_SHIFT - PAGE_SHIFT);
>
*nr += 1 << (PMD_SHIFT - PAGE_SHIFT); ---> *nr += 1U << (PMD_SHIFT -
PAGE_SHIFT);
as it used to be?
> + continue;
> + }
> + }
> + err = vmap_pages_pte_range(pmd, addr, next, prot, pages, nr,
> mask, shift);
> + if (err)
> + return err;
> } while (pmd++, addr = next, addr != end);
> return 0;
> }
>
> static int vmap_pages_pud_range(p4d_t *p4d, unsigned long addr,
> unsigned long end, pgprot_t prot, struct page **pages, int *nr,
> - pgtbl_mod_mask *mask)
> + pgtbl_mod_mask *mask, unsigned int shift)
> {
> pud_t *pud;
> unsigned long next;
> + int err;
>
> pud = pud_alloc_track(&init_mm, p4d, addr, mask);
> if (!pud)
> return -ENOMEM;
> do {
> next = pud_addr_end(addr, end);
> - if (vmap_pages_pmd_range(pud, addr, next, prot, pages, nr,
> mask))
> - return -ENOMEM;
> + err = vmap_pages_pmd_range(pud, addr, next, prot, pages, nr,
> mask, shift);
> + if (err)
> + return err;
> } while (pud++, addr = next, addr != end);
> return 0;
> }
>
> static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr,
> unsigned long end, pgprot_t prot, struct page **pages, int *nr,
> - pgtbl_mod_mask *mask)
> + pgtbl_mod_mask *mask, unsigned int shift)
> {
> p4d_t *p4d;
> unsigned long next;
> + int err;
>
> p4d = p4d_alloc_track(&init_mm, pgd, addr, mask);
> if (!p4d)
> return -ENOMEM;
> do {
> next = p4d_addr_end(addr, end);
> - if (vmap_pages_pud_range(p4d, addr, next, prot, pages, nr,
> mask))
> - return -ENOMEM;
> + err = vmap_pages_pud_range(p4d, addr, next, prot, pages, nr,
> mask, shift);
> + if (err)
> + return err;
> } while (p4d++, addr = next, addr != end);
> return 0;
> }
>
> -static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long
> end,
> - pgprot_t prot, struct page **pages)
> +/*
> + * It can take an array of pages which are not all contiguous, but it
> + * may have contiguous chunks, as hinted by @shift.
> + */
> +static int vmap_pages_range_noflush_walk(unsigned long addr, unsigned long
> end,
> + pgprot_t prot, struct page **pages, unsigned int shift)
> {
> unsigned long start = addr;
> pgd_t *pgd;
> @@ -670,7 +701,7 @@ static int vmap_small_pages_range_noflush(unsigned long
> addr, unsigned long end,
> next = pgd_addr_end(addr, end);
> if (pgd_bad(*pgd))
> mask |= PGTBL_PGD_MODIFIED;
> - err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr,
> &mask);
> + err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr,
> &mask, shift);
> if (err)
> break;
> } while (pgd++, addr = next, addr != end);
> @@ -693,27 +724,12 @@ static int vmap_small_pages_range_noflush(unsigned long
> addr, unsigned long end,
> int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
> pgprot_t prot, struct page **pages, unsigned int page_shift)
> {
> - unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
> -
> WARN_ON(page_shift < PAGE_SHIFT);
>
This is not about this patch but probably on that WARN_ON we should bail out
early.
--
Uladzislau Rezki
