[RFC PATCH v4 16/16] mm: Remove CONFIG_ARCH_HAS_HUGEPD

From: Christophe Leroy
Date: Mon May 27 2024 - 09:35:18 EST

powerpc was the only user of CONFIG_ARCH_HAS_HUGEPD and doesn't
use it anymore, so remove all related code.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
v4: Rebased on v6.10-rc1
---
arch/powerpc/mm/hugetlbpage.c | 1 -
include/linux/hugetlb.h | 6 --
mm/Kconfig | 10 --
mm/gup.c | 183 +---------------------------------
mm/pagewalk.c | 57 +----------
5 files changed, 9 insertions(+), 248 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 76846c6014e4..6b043180220a 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -78,7 +78,6 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,

return pte_alloc_huge(mm, pmd, addr);
}
-#endif

#ifdef CONFIG_PPC_BOOK3S_64
/*
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2b3c3a404769..58daf7d14bf4 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -20,12 +20,6 @@ struct user_struct;
struct mmu_gather;
struct node;

-#ifndef CONFIG_ARCH_HAS_HUGEPD
-typedef struct { unsigned long pd; } hugepd_t;
-#define is_hugepd(hugepd) (0)
-#define __hugepd(x) ((hugepd_t) { (x) })
-#endif
-
void free_huge_folio(struct folio *folio);

#ifdef CONFIG_HUGETLB_PAGE
diff --git a/mm/Kconfig b/mm/Kconfig
index b4cb45255a54..049d29ec6e20 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1119,16 +1119,6 @@ config DMAPOOL_TEST
config ARCH_HAS_PTE_SPECIAL
bool

-#
-# Some architectures require a special hugepage directory format that is
-# required to support multiple hugepage sizes. For example a4fe3ce76
-# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
-# introduced it on powerpc. This allows for a more flexible hugepage
-# pagetable layouts.
-#
-config ARCH_HAS_HUGEPD
- bool
-
config MAPPING_DIRTY_HELPERS
bool

diff --git a/mm/gup.c b/mm/gup.c
index 53ebb0ae53a0..f8e982a42bba 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -501,7 +501,7 @@ static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)

#ifdef CONFIG_MMU

-#if defined(CONFIG_ARCH_HAS_HUGEPD) || defined(CONFIG_HAVE_GUP_FAST)
+#ifdef CONFIG_HAVE_GUP_FAST
static int record_subpages(struct page *page, unsigned long sz,
unsigned long addr, unsigned long end,
struct page **pages)
@@ -515,147 +515,7 @@ static int record_subpages(struct page *page, unsigned long sz,

return nr;
}
-#endif /* CONFIG_ARCH_HAS_HUGEPD || CONFIG_HAVE_GUP_FAST */
-
-#ifdef CONFIG_ARCH_HAS_HUGEPD
-static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
- unsigned long sz)
-{
- unsigned long __boundary = (addr + sz) & ~(sz-1);
- return (__boundary - 1 < end - 1) ? __boundary : end;
-}
-
-/*
- * Returns 1 if succeeded, 0 if failed, -EMLINK if unshare needed.
- *
- * NOTE: for the same entry, gup-fast and gup-slow can return different
- * results (0 v.s. -EMLINK) depending on whether vma is available. This is
- * the expected behavior, where we simply want gup-fast to fallback to
- * gup-slow to take the vma reference first.
- */
-static int gup_hugepte(struct vm_area_struct *vma, pte_t *ptep, unsigned long sz,
- unsigned long addr, unsigned long end, unsigned int flags,
- struct page **pages, int *nr)
-{
- unsigned long pte_end;
- struct page *page;
- struct folio *folio;
- pte_t pte;
- int refs;
-
- pte_end = (addr + sz) & ~(sz-1);
- if (pte_end < end)
- end = pte_end;
-
- pte = huge_ptep_get(vma->mm, addr, ptep);
-
- if (!pte_access_permitted(pte, flags & FOLL_WRITE))
- return 0;
-
- /* hugepages are never "special" */
- VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
-
- page = pte_page(pte);
- refs = record_subpages(page, sz, addr, end, pages + *nr);
-
- folio = try_grab_folio(page, refs, flags);
- if (!folio)
- return 0;
-
- if (unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
- gup_put_folio(folio, refs, flags);
- return 0;
- }
-
- if (!pte_write(pte) && gup_must_unshare(vma, flags, &folio->page)) {
- gup_put_folio(folio, refs, flags);
- return -EMLINK;
- }
-
- *nr += refs;
- folio_set_referenced(folio);
- return 1;
-}
-
-/*
- * NOTE: currently GUP for a hugepd is only possible on hugetlbfs file
- * systems on Power, which does not have issue with folio writeback against
- * GUP updates. When hugepd will be extended to support non-hugetlbfs or
- * even anonymous memory, we need to do extra check as what we do with most
- * of the other folios. See writable_file_mapping_allowed() and
- * gup_fast_folio_allowed() for more information.
- */
-static int gup_hugepd(struct vm_area_struct *vma, hugepd_t hugepd,
- unsigned long addr, unsigned int pdshift,
- unsigned long end, unsigned int flags,
- struct page **pages, int *nr)
-{
- pte_t *ptep;
- unsigned long sz = 1UL << hugepd_shift(hugepd);
- unsigned long next;
- int ret;
-
- ptep = hugepte_offset(hugepd, addr, pdshift);
- do {
- next = hugepte_addr_end(addr, end, sz);
- ret = gup_hugepte(vma, ptep, sz, addr, end, flags, pages, nr);
- if (ret != 1)
- return ret;
- } while (ptep++, addr = next, addr != end);
-
- return 1;
-}
-
-static struct page *follow_hugepd(struct vm_area_struct *vma, hugepd_t hugepd,
- unsigned long addr, unsigned int pdshift,
- unsigned int flags,
- struct follow_page_context *ctx)
-{
- struct page *page;
- struct hstate *h;
- spinlock_t *ptl;
- int nr = 0, ret;
- pte_t *ptep;
-
- /* Only hugetlb supports hugepd */
- if (WARN_ON_ONCE(!is_vm_hugetlb_page(vma)))
- return ERR_PTR(-EFAULT);
-
- h = hstate_vma(vma);
- ptep = hugepte_offset(hugepd, addr, pdshift);
- ptl = huge_pte_lock(h, vma->vm_mm, ptep);
- ret = gup_hugepd(vma, hugepd, addr, pdshift, addr + PAGE_SIZE,
- flags, &page, &nr);
- spin_unlock(ptl);
-
- if (ret == 1) {
- /* GUP succeeded */
- WARN_ON_ONCE(nr != 1);
- ctx->page_mask = (1U << huge_page_order(h)) - 1;
- return page;
- }
-
- /* ret can be either 0 (translates to NULL) or negative */
- return ERR_PTR(ret);
-}
-#else /* CONFIG_ARCH_HAS_HUGEPD */
-static inline int gup_hugepd(struct vm_area_struct *vma, hugepd_t hugepd,
- unsigned long addr, unsigned int pdshift,
- unsigned long end, unsigned int flags,
- struct page **pages, int *nr)
-{
- return 0;
-}
-
-static struct page *follow_hugepd(struct vm_area_struct *vma, hugepd_t hugepd,
- unsigned long addr, unsigned int pdshift,
- unsigned int flags,
- struct follow_page_context *ctx)
-{
- return NULL;
-}
-#endif /* CONFIG_ARCH_HAS_HUGEPD */
-
+#endif /* CONFIG_HAVE_GUP_FAST */

static struct page *no_page_table(struct vm_area_struct *vma,
unsigned int flags, unsigned long address)
@@ -1025,9 +885,6 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
return no_page_table(vma, flags, address);
if (!pmd_present(pmdval))
return no_page_table(vma, flags, address);
- if (unlikely(is_hugepd(__hugepd(pmd_val(pmdval)))))
- return follow_hugepd(vma, __hugepd(pmd_val(pmdval)),
- address, PMD_SHIFT, flags, ctx);
if (pmd_devmap(pmdval)) {
ptl = pmd_lock(mm, pmd);
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
@@ -1078,9 +935,6 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
pud = READ_ONCE(*pudp);
if (!pud_present(pud))
return no_page_table(vma, flags, address);
- if (unlikely(is_hugepd(__hugepd(pud_val(pud)))))
- return follow_hugepd(vma, __hugepd(pud_val(pud)),
- address, PUD_SHIFT, flags, ctx);
if (pud_leaf(pud)) {
ptl = pud_lock(mm, pudp);
page = follow_huge_pud(vma, address, pudp, flags, ctx);
@@ -1106,10 +960,6 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
p4d = READ_ONCE(*p4dp);
BUILD_BUG_ON(p4d_leaf(p4d));

- if (unlikely(is_hugepd(__hugepd(p4d_val(p4d)))))
- return follow_hugepd(vma, __hugepd(p4d_val(p4d)),
- address, P4D_SHIFT, flags, ctx);
-
if (!p4d_present(p4d) || p4d_bad(p4d))
return no_page_table(vma, flags, address);

@@ -1153,10 +1003,7 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
ctx->page_mask = 0;
pgd = pgd_offset(mm, address);

- if (unlikely(is_hugepd(__hugepd(pgd_val(*pgd)))))
- page = follow_hugepd(vma, __hugepd(pgd_val(*pgd)),
- address, PGDIR_SHIFT, flags, ctx);
- else if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+ if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
page = no_page_table(vma, flags, address);
else
page = follow_p4d_mask(vma, address, pgd, flags, ctx);
@@ -3270,14 +3117,6 @@ static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
pages, nr))
return 0;

- } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
- /*
- * architecture have different format for hugetlbfs
- * pmd format and THP pmd format
- */
- if (gup_hugepd(NULL, __hugepd(pmd_val(pmd)), addr,
- PMD_SHIFT, next, flags, pages, nr) != 1)
- return 0;
} else if (!gup_fast_pte_range(pmd, pmdp, addr, next, flags,
pages, nr))
return 0;
@@ -3304,10 +3143,6 @@ static int gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr,
if (!gup_fast_pud_leaf(pud, pudp, addr, next, flags,
pages, nr))
return 0;
- } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
- if (gup_hugepd(NULL, __hugepd(pud_val(pud)), addr,
- PUD_SHIFT, next, flags, pages, nr) != 1)
- return 0;
} else if (!gup_fast_pmd_range(pudp, pud, addr, next, flags,
pages, nr))
return 0;
@@ -3331,12 +3166,8 @@ static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
if (!p4d_present(p4d))
return 0;
BUILD_BUG_ON(p4d_leaf(p4d));
- if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
- if (gup_hugepd(NULL, __hugepd(p4d_val(p4d)), addr,
- P4D_SHIFT, next, flags, pages, nr) != 1)
- return 0;
- } else if (!gup_fast_pud_range(p4dp, p4d, addr, next, flags,
- pages, nr))
+ if (!gup_fast_pud_range(p4dp, p4d, addr, next, flags,
+ pages, nr))
return 0;
} while (p4dp++, addr = next, addr != end);

@@ -3360,10 +3191,6 @@ static void gup_fast_pgd_range(unsigned long addr, unsigned long end,
if (!gup_fast_pgd_leaf(pgd, pgdp, addr, next, flags,
pages, nr))
return;
- } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
- if (gup_hugepd(NULL, __hugepd(pgd_val(pgd)), addr,
- PGDIR_SHIFT, next, flags, pages, nr) != 1)
- return;
} else if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
pages, nr))
return;
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index f46c80b18ce4..ae2f08ce991b 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -73,45 +73,6 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
return err;
}

-#ifdef CONFIG_ARCH_HAS_HUGEPD
-static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
- unsigned long end, struct mm_walk *walk, int pdshift)
-{
- int err = 0;
- const struct mm_walk_ops *ops = walk->ops;
- int shift = hugepd_shift(*phpd);
- int page_size = 1 << shift;
-
- if (!ops->pte_entry)
- return 0;
-
- if (addr & (page_size - 1))
- return 0;
-
- for (;;) {
- pte_t *pte;
-
- spin_lock(&walk->mm->page_table_lock);
- pte = hugepte_offset(*phpd, addr, pdshift);
- err = ops->pte_entry(pte, addr, addr + page_size, walk);
- spin_unlock(&walk->mm->page_table_lock);
-
- if (err)
- break;
- if (addr >= end - page_size)
- break;
- addr += page_size;
- }
- return err;
-}
-#else
-static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
- unsigned long end, struct mm_walk *walk, int pdshift)
-{
- return 0;
-}
-#endif
-
static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
@@ -159,10 +120,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
if (walk->vma)
split_huge_pmd(walk->vma, pmd, addr);

- if (is_hugepd(__hugepd(pmd_val(*pmd))))
- err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
- else
- err = walk_pte_range(pmd, addr, next, walk);
+ err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;

@@ -215,10 +173,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
if (pud_none(*pud))
goto again;

- if (is_hugepd(__hugepd(pud_val(*pud))))
- err = walk_hugepd_range((hugepd_t *)pud, addr, next, walk, PUD_SHIFT);
- else
- err = walk_pmd_range(pud, addr, next, walk);
+ err = walk_pmd_range(pud, addr, next, walk);
if (err)
break;
} while (pud++, addr = next, addr != end);
@@ -250,9 +205,7 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
if (err)
break;
}
- if (is_hugepd(__hugepd(p4d_val(*p4d))))
- err = walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT);
- else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
+ if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
err = walk_pud_range(p4d, addr, next, walk);
if (err)
break;
@@ -287,9 +240,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
if (err)
break;
}
- if (is_hugepd(__hugepd(pgd_val(*pgd))))
- err = walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIFT);
- else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
+ if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
err = walk_p4d_range(pgd, addr, next, walk);
if (err)
break;
--
2.44.0