[PATCH 2/4] mm: hugetlb_vmemmap: use walk_page_range_novma() to simplify the code

Muchun Song
2023-11-27T08:47:31Z

It is unnecessary to implement a series of dedicated page table walking
helpers since there is already a general one walk_page_range_novma().
So use it to simplify the code.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/hugetlb_vmemmap.c | 148 ++++++++++++-------------------------------
1 file changed, 39 insertions(+), 109 deletions(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 87818ee7f01d7..ef14356855d13 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -14,6 +14,7 @@
#include <linux/moduleparam.h>
#include <linux/bootmem_info.h>
#include <linux/mmdebug.h>
+#include <linux/pagewalk.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include "hugetlb_vmemmap.h"
@@ -45,21 +46,14 @@ struct vmemmap_remap_walk {
unsigned long flags;
};

-static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, bool flush)
+static int vmemmap_split_pmd(pmd_t *pmd, struct page *head, unsigned long start,
+ struct vmemmap_remap_walk *walk)
{
pmd_t __pmd;
int i;
unsigned long addr = start;
- struct page *head;
pte_t *pgtable;

- spin_lock(&init_mm.page_table_lock);
- head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL;
- spin_unlock(&init_mm.page_table_lock);
-
- if (!head)
- return 0;
-
pgtable = pte_alloc_one_kernel(&init_mm);
if (!pgtable)
return -ENOMEM;
@@ -88,7 +82,7 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, bool flush)
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
pmd_populate_kernel(&init_mm, pmd, pgtable);
- if (flush)
+ if (!(walk->flags & VMEMMAP_SPLIT_NO_TLB_FLUSH))
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
pte_free_kernel(&init_mm, pgtable);
@@ -98,123 +92,59 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, bool flush)
return 0;
}

-static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
- unsigned long end,
- struct vmemmap_remap_walk *walk)
-{
- pte_t *pte = pte_offset_kernel(pmd, addr);
-
- /*
- * The reuse_page is found 'first' in table walk before we start
- * remapping (which is calling @walk->remap_pte).
- */
- if (!walk->reuse_page) {
- walk->reuse_page = pte_page(ptep_get(pte));
- /*
- * Because the reuse address is part of the range that we are
- * walking, skip the reuse address range.
- */
- addr += PAGE_SIZE;
- pte++;
- walk->nr_walked++;
- }
-
- for (; addr != end; addr += PAGE_SIZE, pte++) {
- walk->remap_pte(pte, addr, walk);
- walk->nr_walked++;
- }
-}
-
-static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
- unsigned long end,
- struct vmemmap_remap_walk *walk)
+static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr,
+ unsigned long next, struct mm_walk *walk)
{
- pmd_t *pmd;
- unsigned long next;
-
- pmd = pmd_offset(pud, addr);
- do {
- int ret;
-
- ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK,
- !(walk->flags & VMEMMAP_SPLIT_NO_TLB_FLUSH));
- if (ret)
- return ret;
+ struct page *head;
+ struct vmemmap_remap_walk *vmemmap_walk = walk->private;

- next = pmd_addr_end(addr, end);
+ /* Only splitting, not remapping the vmemmap pages. */
+ if (!vmemmap_walk->remap_pte)
+ walk->action = ACTION_CONTINUE;

- /*
- * We are only splitting, not remapping the hugetlb vmemmap
- * pages.
- */
- if (!walk->remap_pte)
- continue;
-
- vmemmap_pte_range(pmd, addr, next, walk);
- } while (pmd++, addr = next, addr != end);
+ spin_lock(&init_mm.page_table_lock);
+ head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL;
+ spin_unlock(&init_mm.page_table_lock);
+ if (!head)
+ return 0;

- return 0;
+ return vmemmap_split_pmd(pmd, head, addr & PMD_MASK, vmemmap_walk);
}

-static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
- unsigned long end,
- struct vmemmap_remap_walk *walk)
+static int vmemmap_pte_entry(pte_t *pte, unsigned long addr,
+ unsigned long next, struct mm_walk *walk)
{
- pud_t *pud;
- unsigned long next;
-
- pud = pud_offset(p4d, addr);
- do {
- int ret;
+ struct vmemmap_remap_walk *vmemmap_walk = walk->private;

- next = pud_addr_end(addr, end);
- ret = vmemmap_pmd_range(pud, addr, next, walk);
- if (ret)
- return ret;
- } while (pud++, addr = next, addr != end);
+ /*
+ * The reuse_page is found 'first' in page table walking before
+ * starting remapping.
+ */
+ if (!vmemmap_walk->reuse_page)
+ vmemmap_walk->reuse_page = pte_page(ptep_get(pte));
+ else
+ vmemmap_walk->remap_pte(pte, addr, vmemmap_walk);
+ vmemmap_walk->nr_walked++;

return 0;
}

-static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
- unsigned long end,
- struct vmemmap_remap_walk *walk)
-{
- p4d_t *p4d;
- unsigned long next;
-
- p4d = p4d_offset(pgd, addr);
- do {
- int ret;
-
- next = p4d_addr_end(addr, end);
- ret = vmemmap_pud_range(p4d, addr, next, walk);
- if (ret)
- return ret;
- } while (p4d++, addr = next, addr != end);
-
- return 0;
-}
+static const struct mm_walk_ops vmemmap_remap_ops = {
+ .pmd_entry = vmemmap_pmd_entry,
+ .pte_entry = vmemmap_pte_entry,
+};

static int vmemmap_remap_range(unsigned long start, unsigned long end,
struct vmemmap_remap_walk *walk)
{
- unsigned long addr = start;
- unsigned long next;
- pgd_t *pgd;
-
- VM_BUG_ON(!PAGE_ALIGNED(start));
- VM_BUG_ON(!PAGE_ALIGNED(end));
+ int ret;

- pgd = pgd_offset_k(addr);
- do {
- int ret;
+ VM_BUG_ON(!PAGE_ALIGNED(start | end));

- next = pgd_addr_end(addr, end);
- ret = vmemmap_p4d_range(pgd, addr, next, walk);
- if (ret)
- return ret;
- } while (pgd++, addr = next, addr != end);
+ ret = walk_page_range_novma(&init_mm, start, end, &vmemmap_remap_ops,
+ NULL, walk);
+ if (ret)
+ return ret;

if (walk->remap_pte && !(walk->flags & VMEMMAP_REMAP_NO_TLB_FLUSH))
flush_tlb_kernel_range(start, end);
--
2.20.1