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Message-ID: <20250630164726.930405-1-gerald.schaefer@linux.ibm.com>
Date: Mon, 30 Jun 2025 18:47:25 +0200
From: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Anshuman Khandual <anshuman.khandual@....com>
Cc: Matthew Wilcox <willy@...radead.org>, David Hildenbrand <david@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
linux-s390 <linux-s390@...r.kernel.org>
Subject: [PATCH] mm/debug_vm_pgtable: Use a swp_entry_t input value for swap tests
The various __pte/pmd_to_swp_entry and __swp_entry_to_pte/pmd helper
functions are expected to operate on swap PTE/PMD entries, not on
present and mapped entries.
Reflect this in the swap tests by using a swp_entry_t as input value,
and convert it to a swap PTE/PMD for testing, similar to how it is already
done in pte_swap_exclusive_tests(). Move the swap entry creation from
there to init_args() and store it in args, so it can also be used in other
functions.
The pte/pmd_swap_tests() are also changed to compare entries instead of
pfn values, again similar to pte_swap_exclusive_tests(). pte/pmd_pfn()
helpers are also not expected to operate on swap PTE/PMD entries at all.
Also update documentation, to reflect that the helpers operate on swap
PTE/PMD entries and not present and mapped entries, and use correct names,
i.e. __swp_to_pte/pmd_entry -> __swp_entry_to_pte/pmd.
For consistency, also change pte/pmd_swap_soft_dirty_tests() to use
args->swp_entry instead of a present and mapped PTE/PMD.
Link: https://lore.kernel.org/all/20250623184321.927418-1-gerald.schaefer@linux.ibm.com
Signed-off-by: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
---
Documentation/mm/arch_pgtable_helpers.rst | 8 ++--
mm/debug_vm_pgtable.c | 53 ++++++++++++++---------
2 files changed, 36 insertions(+), 25 deletions(-)
diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst
index c88c7fa665d6..ba2f658bc241 100644
--- a/Documentation/mm/arch_pgtable_helpers.rst
+++ b/Documentation/mm/arch_pgtable_helpers.rst
@@ -236,13 +236,13 @@ SWAP Page Table Helpers
========================
+---------------------------+--------------------------------------------------+
-| __pte_to_swp_entry | Creates a swapped entry (arch) from a mapped PTE |
+| __pte_to_swp_entry | Creates a swp_entry_t (arch) from a swap PTE |
+---------------------------+--------------------------------------------------+
-| __swp_to_pte_entry | Creates a mapped PTE from a swapped entry (arch) |
+| __swp_entry_to_pte | Creates a swap PTE from a swp_entry_t (arch) |
+---------------------------+--------------------------------------------------+
-| __pmd_to_swp_entry | Creates a swapped entry (arch) from a mapped PMD |
+| __pmd_to_swp_entry | Creates a swp_entry_t (arch) from a swap PMD |
+---------------------------+--------------------------------------------------+
-| __swp_to_pmd_entry | Creates a mapped PMD from a swapped entry (arch) |
+| __swp_entry_to_pmd | Creates a swap PMD from a swp_entry_t (arch) |
+---------------------------+--------------------------------------------------+
| is_migration_entry | Tests a migration (read or write) swapped entry |
+-------------------------------+----------------------------------------------+
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index bd8f9317b025..d19031f275a3 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -72,6 +72,8 @@ struct pgtable_debug_args {
unsigned long fixed_pud_pfn;
unsigned long fixed_pmd_pfn;
unsigned long fixed_pte_pfn;
+
+ swp_entry_t swp_entry;
};
static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx)
@@ -698,12 +700,15 @@ static void __init pte_soft_dirty_tests(struct pgtable_debug_args *args)
static void __init pte_swap_soft_dirty_tests(struct pgtable_debug_args *args)
{
- pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+ pte_t pte;
if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
return;
pr_debug("Validating PTE swap soft dirty\n");
+ pte = swp_entry_to_pte(args->swp_entry);
+ WARN_ON(!is_swap_pte(pte));
+
WARN_ON(!pte_swp_soft_dirty(pte_swp_mksoft_dirty(pte)));
WARN_ON(pte_swp_soft_dirty(pte_swp_clear_soft_dirty(pte)));
}
@@ -737,7 +742,9 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args)
return;
pr_debug("Validating PMD swap soft dirty\n");
- pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+ pmd = swp_entry_to_pmd(args->swp_entry);
+ WARN_ON(!is_swap_pmd(pmd));
+
WARN_ON(!pmd_swp_soft_dirty(pmd_swp_mksoft_dirty(pmd)));
WARN_ON(pmd_swp_soft_dirty(pmd_swp_clear_soft_dirty(pmd)));
}
@@ -748,17 +755,11 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) {
static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args)
{
- unsigned long max_swap_offset;
swp_entry_t entry, entry2;
pte_t pte;
pr_debug("Validating PTE swap exclusive\n");
-
- /* See generic_max_swapfile_size(): probe the maximum offset */
- max_swap_offset = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0, ~0UL))));
-
- /* Create a swp entry with all possible bits set */
- entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, max_swap_offset);
+ entry = args->swp_entry;
pte = swp_entry_to_pte(entry);
WARN_ON(pte_swp_exclusive(pte));
@@ -782,30 +783,34 @@ static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args)
static void __init pte_swap_tests(struct pgtable_debug_args *args)
{
- swp_entry_t swp;
- pte_t pte;
+ swp_entry_t arch_entry;
+ pte_t pte1, pte2;
pr_debug("Validating PTE swap\n");
- pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
- swp = __pte_to_swp_entry(pte);
- pte = __swp_entry_to_pte(swp);
- WARN_ON(args->fixed_pte_pfn != pte_pfn(pte));
+ pte1 = swp_entry_to_pte(args->swp_entry);
+ WARN_ON(!is_swap_pte(pte1));
+
+ arch_entry = __pte_to_swp_entry(pte1);
+ pte2 = __swp_entry_to_pte(arch_entry);
+ WARN_ON(memcmp(&pte1, &pte2, sizeof(pte1)));
}
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
static void __init pmd_swap_tests(struct pgtable_debug_args *args)
{
- swp_entry_t swp;
- pmd_t pmd;
+ swp_entry_t arch_entry;
+ pmd_t pmd1, pmd2;
if (!has_transparent_hugepage())
return;
pr_debug("Validating PMD swap\n");
- pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
- swp = __pmd_to_swp_entry(pmd);
- pmd = __swp_entry_to_pmd(swp);
- WARN_ON(args->fixed_pmd_pfn != pmd_pfn(pmd));
+ pmd1 = swp_entry_to_pmd(args->swp_entry);
+ WARN_ON(!is_swap_pmd(pmd1));
+
+ arch_entry = __pmd_to_swp_entry(pmd1);
+ pmd2 = __swp_entry_to_pmd(arch_entry);
+ WARN_ON(memcmp(&pmd1, &pmd2, sizeof(pmd1)));
}
#else /* !CONFIG_ARCH_ENABLE_THP_MIGRATION */
static void __init pmd_swap_tests(struct pgtable_debug_args *args) { }
@@ -1110,6 +1115,7 @@ static void __init init_fixed_pfns(struct pgtable_debug_args *args)
static int __init init_args(struct pgtable_debug_args *args)
{
+ unsigned long max_swap_offset;
struct page *page = NULL;
int ret = 0;
@@ -1192,6 +1198,11 @@ static int __init init_args(struct pgtable_debug_args *args)
init_fixed_pfns(args);
+ /* See generic_max_swapfile_size(): probe the maximum offset */
+ max_swap_offset = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0, ~0UL))));
+ /* Create a swp entry with all possible bits set */
+ args->swp_entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, max_swap_offset);
+
/*
* Allocate (huge) pages because some of the tests need to access
* the data in the pages. The corresponding tests will be skipped
--
2.48.1
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