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mm/pagewalk: drop FW_MIGRATION

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We removed the last user of FW_MIGRATION in commit 912aa82595 ("Revert
"mm/ksm: convert break_ksm() from walk_page_range_vma() to folio_walk"").

So let's remove FW_MIGRATION and assign FW_ZEROPAGE bit 0.  Including
leafops.h is no longer required.

While at it, convert "expose_page" to "zeropage", as zeropages are now the
only remaining use case for not exposing a page.

Link: https://lkml.kernel.org/r/20260227212952.190691-1-david@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand (Arm)
2026-02-27 22:29:52 +01:00
committed by Andrew Morton
parent 22aa332199
commit 99573ef4ac
2 changed files with 9 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/pagewalk.h
View File

@@ -148,14 +148,8 @@ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
typedef int __bitwise folio_walk_flags_t;
/*
* Walk migration entries as well. Careful: a large folio might get split
* concurrently.
*/
#define FW_MIGRATION ((__force folio_walk_flags_t)BIT(0))
/* Walk shared zeropages (small + huge) as well. */
#define FW_ZEROPAGE ((__force folio_walk_flags_t)BIT(1))
#define FW_ZEROPAGE ((__force folio_walk_flags_t)BIT(0))
enum folio_walk_level {
FW_LEVEL_PTE,

40
mm/pagewalk.c
View File

@@ -5,7 +5,6 @@
#include <linux/hugetlb.h>
#include <linux/mmu_context.h>
#include <linux/swap.h>
#include <linux/leafops.h>
#include <asm/tlbflush.h>
@@ -841,9 +840,6 @@ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
* VM as documented by vm_normal_page(). If requested, zeropages will be
* returned as well.
*
* As default, this function only considers present page table entries.
* If requested, it will also consider migration entries.
*
* If this function returns NULL it might either indicate "there is nothing" or
* "there is nothing suitable".
*
@@ -854,11 +850,10 @@ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
* that call.
*
* @fw->page will correspond to the page that is effectively referenced by
* @addr. However, for migration entries and shared zeropages @fw->page is
* set to NULL. Note that large folios might be mapped by multiple page table
* entries, and this function will always only lookup a single entry as
* specified by @addr, which might or might not cover more than a single page of
* the returned folio.
* @addr. However, for shared zeropages @fw->page is set to NULL. Note that
* large folios might be mapped by multiple page table entries, and this
* function will always only lookup a single entry as specified by @addr, which
* might or might not cover more than a single page of the returned folio.
*
* This function must *not* be used as a naive replacement for
* get_user_pages() / pin_user_pages(), especially not to perform DMA or
@@ -885,7 +880,7 @@ struct folio *folio_walk_start(struct folio_walk *fw,
folio_walk_flags_t flags)
{
unsigned long entry_size;
bool expose_page = true;
bool zeropage = false;
struct page *page;
pud_t *pudp, pud;
pmd_t *pmdp, pmd;
@@ -933,10 +928,6 @@ struct folio *folio_walk_start(struct folio_walk *fw,
if (page)
goto found;
}
/*
* TODO: FW_MIGRATION support for PUD migration entries
* once there are relevant users.
*/
spin_unlock(ptl);
goto not_found;
}
@@ -970,16 +961,9 @@ pmd_table:
} else if ((flags & FW_ZEROPAGE) &&
is_huge_zero_pmd(pmd)) {
page = pfn_to_page(pmd_pfn(pmd));
expose_page = false;
zeropage = true;
goto found;
}
} else if ((flags & FW_MIGRATION) &&
pmd_is_migration_entry(pmd)) {
const softleaf_t entry = softleaf_from_pmd(pmd);
page = softleaf_to_page(entry);
expose_page = false;
goto found;
}
spin_unlock(ptl);
goto not_found;
@@ -1004,15 +988,7 @@ pte_table:
if ((flags & FW_ZEROPAGE) &&
is_zero_pfn(pte_pfn(pte))) {
page = pfn_to_page(pte_pfn(pte));
expose_page = false;
goto found;
}
} else if (!pte_none(pte)) {
const softleaf_t entry = softleaf_from_pte(pte);
if ((flags & FW_MIGRATION) && softleaf_is_migration(entry)) {
page = softleaf_to_page(entry);
expose_page = false;
zeropage = true;
goto found;
}
}
@@ -1021,7 +997,7 @@ not_found:
vma_pgtable_walk_end(vma);
return NULL;
found:
if (expose_page)
if (!zeropage)
/* Note: Offset from the mapped page, not the folio start. */
fw->page = page + ((addr & (entry_size - 1)) >> PAGE_SHIFT);
else