* + mm-gup-remove-dead-pgmap-refcounting-code.patch added to mm-new branch
@ 2025-09-05 0:40 Andrew Morton
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From: Andrew Morton @ 2025-09-05 0:40 UTC (permalink / raw)
To: mm-commits, peterx, osalvador, jhubbard, jgg, david,
dan.j.williams, apopple, akpm
The patch titled
Subject: mm/gup: remove dead pgmap refcounting code
has been added to the -mm mm-new branch. Its filename is
mm-gup-remove-dead-pgmap-refcounting-code.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-remove-dead-pgmap-refcounting-code.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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patches, and acceptance into mm-new is a notification for others take
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Alistair Popple <apopple@nvidia.com>
Subject: mm/gup: remove dead pgmap refcounting code
Date: Thu, 4 Sep 2025 08:59:25 +1000
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>
Cc: 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>
---
mm/gup.c | 67 ++++++++++++++++++++---------------------------------
1 file changed, 26 insertions(+), 41 deletions(-)
--- a/mm/gup.c~mm-gup-remove-dead-pgmap-refcounting-code
+++ a/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(
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(stru
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(
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(stru
#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(stru
#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(stru
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(
}
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(stru
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(stru
}
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(stru
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(stru
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(stru
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(stru
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(stru
* @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(stru
*/
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(str
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_s
{
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_s
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;
}
@@ -2849,7 +2837,6 @@ static int gup_fast_pte_range(pmd_t pmd,
unsigned long end, unsigned int flags, struct page **pages,
int *nr)
{
- struct dev_pagemap *pgmap = NULL;
int ret = 0;
pte_t *ptep, *ptem;
@@ -2922,8 +2909,6 @@ static int gup_fast_pte_range(pmd_t pmd,
ret = 1;
pte_unmap:
- if (pgmap)
- put_dev_pagemap(pgmap);
pte_unmap(ptem);
return ret;
}
_
Patches currently in -mm which might be from apopple@nvidia.com are
mm-gup-remove-dead-pgmap-refcounting-code.patch
mm-memremap-remove-unused-get_dev_pagemap-parameter.patch
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