mm/gup: remove dead pgmap refcounting code

Prior to commit aed877c2b425 ("device/dax: properly refcount device dax
pages when mapping") ZONE_DEVICE pages were not fully reference counted
when mapped into user page tables.  Instead GUP would take a reference on
the associated pgmap to ensure the results of pfn_to_page() remained
valid.

This is no longer required and most of the code was removed by commit
fd2825b0760a ("mm/gup: remove pXX_devmap usage from get_user_pages()").
Finish cleaning this up by removing the dead calls to put_dev_pagemap()
and the temporary context struct.

Link: https://lkml.kernel.org/r/20250903225926.34702-1-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 83438bbbf2f6aa89ac6b33c0eb0fc91ac2a49060..00f30e03f7363155fd1a9bf76ee18fa0f87d56f6 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -28,11 +28,6 @@
 #include "internal.h"
 #include "swap.h"
 
-struct follow_page_context {
-       struct dev_pagemap *pgmap;
-       unsigned int page_mask;
-};
-
 static inline void sanity_check_pinned_pages(struct page **pages,
                                             unsigned long npages)
 {
@@ -653,7 +648,7 @@ static inline bool can_follow_write_pud(pud_t pud, struct page *page,
 
 static struct page *follow_huge_pud(struct vm_area_struct *vma,
                                    unsigned long addr, pud_t *pudp,
-                                   int flags, struct follow_page_context *ctx)
+                                   int flags, unsigned long *page_mask)
 {
        struct mm_struct *mm = vma->vm_mm;
        struct page *page;
@@ -680,7 +675,7 @@ static struct page *follow_huge_pud(struct vm_area_struct *vma,
        if (ret)
                page = ERR_PTR(ret);
        else
-               ctx->page_mask = HPAGE_PUD_NR - 1;
+               *page_mask = HPAGE_PUD_NR - 1;
 
        return page;
 }
@@ -706,7 +701,7 @@ static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
 static struct page *follow_huge_pmd(struct vm_area_struct *vma,
                                    unsigned long addr, pmd_t *pmd,
                                    unsigned int flags,
-                                   struct follow_page_context *ctx)
+                                   unsigned long *page_mask)
 {
        struct mm_struct *mm = vma->vm_mm;
        pmd_t pmdval = *pmd;
@@ -743,7 +738,7 @@ static struct page *follow_huge_pmd(struct vm_area_struct *vma,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
        page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
-       ctx->page_mask = HPAGE_PMD_NR - 1;
+       *page_mask = HPAGE_PMD_NR - 1;
 
        return page;
 }
@@ -751,7 +746,7 @@ static struct page *follow_huge_pmd(struct vm_area_struct *vma,
 #else  /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */
 static struct page *follow_huge_pud(struct vm_area_struct *vma,
                                    unsigned long addr, pud_t *pudp,
-                                   int flags, struct follow_page_context *ctx)
+                                   int flags, unsigned long *page_mask)
 {
        return NULL;
 }
@@ -759,7 +754,7 @@ static struct page *follow_huge_pud(struct vm_area_struct *vma,
 static struct page *follow_huge_pmd(struct vm_area_struct *vma,
                                    unsigned long addr, pmd_t *pmd,
                                    unsigned int flags,
-                                   struct follow_page_context *ctx)
+                                   unsigned long *page_mask)
 {
        return NULL;
 }
@@ -805,8 +800,7 @@ static inline bool can_follow_write_pte(pte_t pte, struct page *page,
 }
 
 static struct page *follow_page_pte(struct vm_area_struct *vma,
-               unsigned long address, pmd_t *pmd, unsigned int flags,
-               struct dev_pagemap **pgmap)
+               unsigned long address, pmd_t *pmd, unsigned int flags)
 {
        struct mm_struct *mm = vma->vm_mm;
        struct folio *folio;
@@ -904,7 +898,7 @@ no_page:
 static struct page *follow_pmd_mask(struct vm_area_struct *vma,
                                    unsigned long address, pud_t *pudp,
                                    unsigned int flags,
-                                   struct follow_page_context *ctx)
+                                   unsigned long *page_mask)
 {
        pmd_t *pmd, pmdval;
        spinlock_t *ptl;
@@ -918,7 +912,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
        if (!pmd_present(pmdval))
                return no_page_table(vma, flags, address);
        if (likely(!pmd_leaf(pmdval)))
-               return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
+               return follow_page_pte(vma, address, pmd, flags);
 
        if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags))
                return no_page_table(vma, flags, address);
@@ -931,16 +925,16 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
        }
        if (unlikely(!pmd_leaf(pmdval))) {
                spin_unlock(ptl);
-               return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
+               return follow_page_pte(vma, address, pmd, flags);
        }
        if (pmd_trans_huge(pmdval) && (flags & FOLL_SPLIT_PMD)) {
                spin_unlock(ptl);
                split_huge_pmd(vma, pmd, address);
                /* If pmd was left empty, stuff a page table in there quickly */
                return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
-                       follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
+                       follow_page_pte(vma, address, pmd, flags);
        }
-       page = follow_huge_pmd(vma, address, pmd, flags, ctx);
+       page = follow_huge_pmd(vma, address, pmd, flags, page_mask);
        spin_unlock(ptl);
        return page;
 }
@@ -948,7 +942,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
 static struct page *follow_pud_mask(struct vm_area_struct *vma,
                                    unsigned long address, p4d_t *p4dp,
                                    unsigned int flags,
-                                   struct follow_page_context *ctx)
+                                   unsigned long *page_mask)
 {
        pud_t *pudp, pud;
        spinlock_t *ptl;
@@ -961,7 +955,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
                return no_page_table(vma, flags, address);
        if (pud_leaf(pud)) {
                ptl = pud_lock(mm, pudp);
-               page = follow_huge_pud(vma, address, pudp, flags, ctx);
+               page = follow_huge_pud(vma, address, pudp, flags, page_mask);
                spin_unlock(ptl);
                if (page)
                        return page;
@@ -970,13 +964,13 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
        if (unlikely(pud_bad(pud)))
                return no_page_table(vma, flags, address);
 
-       return follow_pmd_mask(vma, address, pudp, flags, ctx);
+       return follow_pmd_mask(vma, address, pudp, flags, page_mask);
 }
 
 static struct page *follow_p4d_mask(struct vm_area_struct *vma,
                                    unsigned long address, pgd_t *pgdp,
                                    unsigned int flags,
-                                   struct follow_page_context *ctx)
+                                   unsigned long *page_mask)
 {
        p4d_t *p4dp, p4d;
 
@@ -987,7 +981,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
        if (!p4d_present(p4d) || p4d_bad(p4d))
                return no_page_table(vma, flags, address);
 
-       return follow_pud_mask(vma, address, p4dp, flags, ctx);
+       return follow_pud_mask(vma, address, p4dp, flags, page_mask);
 }
 
 /**
@@ -995,20 +989,16 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
  * @vma: vm_area_struct mapping @address
  * @address: virtual address to look up
  * @flags: flags modifying lookup behaviour
- * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
- *       pointer to output page_mask
+ * @page_mask: a pointer to output page_mask
  *
  * @flags can have FOLL_ flags set, defined in <linux/mm.h>
  *
- * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
- * the device's dev_pagemap metadata to avoid repeating expensive lookups.
- *
  * When getting an anonymous page and the caller has to trigger unsharing
  * of a shared anonymous page first, -EMLINK is returned. The caller should
  * trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only
  * relevant with FOLL_PIN and !FOLL_WRITE.
  *
- * On output, the @ctx->page_mask is set according to the size of the page.
+ * On output, @page_mask is set according to the size of the page.
  *
  * Return: the mapped (struct page *), %NULL if no mapping exists, or
  * an error pointer if there is a mapping to something not represented
@@ -1016,7 +1006,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
  */
 static struct page *follow_page_mask(struct vm_area_struct *vma,
                              unsigned long address, unsigned int flags,
-                             struct follow_page_context *ctx)
+                             unsigned long *page_mask)
 {
        pgd_t *pgd;
        struct mm_struct *mm = vma->vm_mm;
@@ -1024,13 +1014,13 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
 
        vma_pgtable_walk_begin(vma);
 
-       ctx->page_mask = 0;
+       *page_mask = 0;
        pgd = pgd_offset(mm, address);
 
        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);
+               page = follow_p4d_mask(vma, address, pgd, flags, page_mask);
 
        vma_pgtable_walk_end(vma);
 
@@ -1368,7 +1358,7 @@ static long __get_user_pages(struct mm_struct *mm,
 {
        long ret = 0, i = 0;
        struct vm_area_struct *vma = NULL;
-       struct follow_page_context ctx = { NULL };
+       unsigned long page_mask = 0;
 
        if (!nr_pages)
                return 0;
@@ -1410,7 +1400,7 @@ static long __get_user_pages(struct mm_struct *mm,
                                                pages ? &page : NULL);
                                if (ret)
                                        goto out;
-                               ctx.page_mask = 0;
+                               page_mask = 0;
                                goto next_page;
                        }
 
@@ -1433,7 +1423,7 @@ retry:
                }
                cond_resched();
 
-               page = follow_page_mask(vma, start, gup_flags, &ctx);
+               page = follow_page_mask(vma, start, gup_flags, &page_mask);
                if (!page || PTR_ERR(page) == -EMLINK) {
                        ret = faultin_page(vma, start, gup_flags,
                                           PTR_ERR(page) == -EMLINK, locked);
@@ -1466,7 +1456,7 @@ retry:
                        goto out;
                }
 next_page:
-               page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
+               page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
                if (page_increm > nr_pages)
                        page_increm = nr_pages;
 
@@ -1516,8 +1506,6 @@ next_page:
                nr_pages -= page_increm;
        } while (nr_pages);
 out:
-       if (ctx.pgmap)
-               put_dev_pagemap(ctx.pgmap);
        return i ? i : ret;
 }
 
@@ -2853,7 +2841,6 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
                unsigned long end, unsigned int flags, struct page **pages,
                int *nr)
 {
-       struct dev_pagemap *pgmap = NULL;
        int ret = 0;
        pte_t *ptep, *ptem;
 
@@ -2926,8 +2913,6 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
        ret = 1;
 
 pte_unmap:
-       if (pgmap)
-               put_dev_pagemap(pgmap);
        pte_unmap(ptem);
        return ret;
 }