From: Usama Arif <usama.arif@linux.dev>
To: Andrew Morton <akpm@linux-foundation.org>,
david@kernel.org, chrisl@kernel.org, kasong@tencent.com,
ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org
Cc: ying.huang@linux.alibaba.com, Baoquan He <baoquan.he@linux.dev>,
willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org,
riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr,
kas@kernel.org, baohua@kernel.org, dev.jain@arm.com,
baolin.wang@linux.alibaba.com, Nico Pache <nico.pache@linux.dev>,
Liam R. Howlett <liam@infradead.org>,
ryan.roberts@arm.com, Vlastimil Babka <vbabka@kernel.org>,
lance.yang@linux.dev, linux-kernel@vger.kernel.org,
nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org,
kernel-team@meta.com, Usama Arif <usama.arif@linux.dev>
Subject: [PATCH v5 01/11] mm: add PMD swap entry detection support
Date: Wed, 22 Jul 2026 08:19:32 -0700 [thread overview]
Message-ID: <20260722152043.2273289-2-usama.arif@linux.dev> (raw)
In-Reply-To: <20260722152043.2273289-1-usama.arif@linux.dev>
Currently when a PMD-mapped THP is swapped out, the PMD is always
split into HPAGE_PMD_NR PTE-level swap entries. To preserve huge
page information across swap cycles, later patches will install a
single PMD-level swap entry instead. Add the infrastructure to detect
those entries.
Teach the softleaf layer to recognise PMD swap entries:
pmd_is_swap_entry() detects them and softleaf_is_valid_pmd_entry()
accepts them as a valid non-present type. Because swap entries do
not encode a PFN, make pmd_to_softleaf_folio() return NULL for them
instead of passing the swap offset to softleaf_to_folio(). Clear
the exclusive overlay bit in softleaf_from_pmd() before decoding,
matching how soft_dirty and uffd bits are already stripped.
Add pmd_swp_mkexclusive(), pmd_swp_exclusive(), and
pmd_swp_clear_exclusive() helpers to each architecture that supports
PMD softleaf entries (x86, arm64, s390, riscv, loongarch, powerpc),
mirroring the existing PTE swap exclusive helpers in each arch's
pgtable.h. Provide generic no-op PMD swap exclusive fallbacks for
architectures without PMD softleaf support, matching the generic PMD
swap soft-dirty fallbacks.
Signed-off-by: Usama Arif <usama.arif@linux.dev>
---
arch/arm64/include/asm/pgtable.h | 6 +++++
arch/loongarch/include/asm/pgtable.h | 19 ++++++++++++++
arch/powerpc/include/asm/book3s/64/pgtable.h | 17 +++++++++++++
arch/riscv/include/asm/pgtable.h | 15 +++++++++++
arch/s390/include/asm/pgtable.h | 17 +++++++++++++
arch/x86/include/asm/pgtable.h | 17 +++++++++++++
include/linux/leafops.h | 26 ++++++++++++++++----
include/linux/pgtable.h | 17 +++++++++++++
8 files changed, 129 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a2681d755358..860f95573d1f 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -598,6 +598,12 @@ static inline int pmd_protnone(pmd_t pmd)
#define pmd_swp_clear_uffd(pmd) \
pte_pmd(pte_swp_clear_uffd(pmd_pte(pmd)))
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+#define pmd_swp_exclusive(pmd) pte_swp_exclusive(pmd_pte(pmd))
+#define pmd_swp_mkexclusive(pmd) pte_pmd(pte_swp_mkexclusive(pmd_pte(pmd)))
+#define pmd_swp_clear_exclusive(pmd) \
+ pte_pmd(pte_swp_clear_exclusive(pmd_pte(pmd)))
+#endif
#define pmd_write(pmd) pte_write(pmd_pte(pmd))
diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index 1952e34bc8ee..aa8e1223d397 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -357,6 +357,25 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
return pte;
}
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ pmd_val(pmd) |= _PAGE_SWP_EXCLUSIVE;
+ return pmd;
+}
+
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+ return pmd_val(pmd) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ pmd_val(pmd) &= ~_PAGE_SWP_EXCLUSIVE;
+ return pmd;
+}
+#endif
+
#define pte_none(pte) (!(pte_val(pte) & ~_PAGE_GLOBAL))
#define pte_present(pte) (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROTNONE))
#define pte_no_exec(pte) (pte_val(pte) & _PAGE_NO_EXEC)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index f4db7d7fbd5c..6a899d0793b3 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -699,6 +699,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
return __pte_raw(pte_raw(pte) & cpu_to_be64(~_PAGE_SWP_EXCLUSIVE));
}
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ return __pmd_raw(pmd_raw(pmd) | cpu_to_be64(_PAGE_SWP_EXCLUSIVE));
+}
+
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+ return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_SWP_EXCLUSIVE));
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ return __pmd_raw(pmd_raw(pmd) & cpu_to_be64(~_PAGE_SWP_EXCLUSIVE));
+}
+#endif
+
static inline bool check_pte_access(unsigned long access, unsigned long ptev)
{
/*
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 7f21742b2b6a..5f53b158a95c 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -1206,6 +1206,21 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
}
#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+ return pte_swp_exclusive(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_mkexclusive(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_clear_exclusive(pmd_pte(pmd)));
+}
+
#define __pmd_to_swp_entry(pmd) ((swp_entry_t) { pmd_val(pmd) })
#define __swp_entry_to_pmd(swp) __pmd((swp).val)
#endif /* CONFIG_ARCH_HAS_PMD_SOFTLEAVES */
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index e882663a58e7..490e4a3464b1 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -870,6 +870,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
return clear_pte_bit(pte, __pgprot(_PAGE_SWP_EXCLUSIVE));
}
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ return set_pmd_bit(pmd, __pgprot(_PAGE_SWP_EXCLUSIVE));
+}
+
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+ return pmd_val(pmd) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ return clear_pmd_bit(pmd, __pgprot(_PAGE_SWP_EXCLUSIVE));
+}
+#endif
+
static inline int pte_soft_dirty(pte_t pte)
{
return pte_val(pte) & _PAGE_SOFT_DIRTY;
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 8e0018fadd14..b5da5447e83d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1525,6 +1525,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
return pte_clear_flags(pte, _PAGE_SWP_EXCLUSIVE);
}
+#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ return pmd_set_flags(pmd, _PAGE_SWP_EXCLUSIVE);
+}
+
+static inline int pmd_swp_exclusive(pmd_t pmd)
+{
+ return pmd_flags(pmd) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ return pmd_clear_flags(pmd, _PAGE_SWP_EXCLUSIVE);
+}
+#endif
+
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
{
diff --git a/include/linux/leafops.h b/include/linux/leafops.h
index 4c1476ae3234..8397193ba399 100644
--- a/include/linux/leafops.h
+++ b/include/linux/leafops.h
@@ -102,6 +102,8 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd)
pmd = pmd_swp_clear_soft_dirty(pmd);
if (pmd_swp_uffd(pmd))
pmd = pmd_swp_clear_uffd(pmd);
+ if (pmd_swp_exclusive(pmd))
+ pmd = pmd_swp_clear_exclusive(pmd);
arch_entry = __pmd_to_swp_entry(pmd);
/* Temporary until swp_entry_t eliminated. */
@@ -634,18 +636,30 @@ static inline bool pmd_is_migration_entry(pmd_t pmd)
*/
static inline bool softleaf_is_valid_pmd_entry(softleaf_t entry)
{
- /* Only device private, migration entries valid for PMD. */
+ /* Device private, migration, and swap entries valid for PMD. */
return softleaf_is_device_private(entry) ||
- softleaf_is_migration(entry);
+ softleaf_is_migration(entry) ||
+ softleaf_is_swap(entry);
+}
+
+/**
+ * pmd_is_swap_entry() - Does this PMD entry encode an actual swap entry?
+ * @pmd: PMD entry.
+ *
+ * Returns: true if the PMD encodes a swap entry, otherwise false.
+ */
+static inline bool pmd_is_swap_entry(pmd_t pmd)
+{
+ return softleaf_is_swap(softleaf_from_pmd(pmd));
}
/**
* pmd_is_valid_softleaf() - Is this PMD entry a valid softleaf entry?
* @pmd: PMD entry.
*
- * PMD leaf entries are valid only if they are device private or migration
- * entries. This function asserts that a PMD leaf entry is valid in this
- * respect.
+ * PMD leaf entries are valid only if they are device private, migration,
+ * or swap entries. This function asserts that a PMD leaf entry is valid
+ * in this respect.
*
* Returns: true if the PMD entry is a valid leaf entry, otherwise false.
*/
@@ -673,6 +687,8 @@ static inline struct folio *pmd_to_softleaf_folio(pmd_t pmd)
VM_WARN_ON_ONCE(true);
return NULL;
}
+ if (!softleaf_has_pfn(entry))
+ return NULL;
return softleaf_to_folio(entry);
}
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 8c093c119e5a..e10a7e91e426 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1917,6 +1917,23 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
}
#endif
+#ifndef CONFIG_ARCH_HAS_PMD_SOFTLEAVES
+static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd)
+{
+ return pmd;
+}
+
+static inline bool pmd_swp_exclusive(pmd_t pmd)
+{
+ return false;
+}
+
+static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd)
+{
+ return pmd;
+}
+#endif
+
#ifndef __HAVE_PFNMAP_TRACKING
/*
* Interfaces that can be used by architecture code to keep track of
--
2.53.0-Meta
next prev parent reply other threads:[~2026-07-22 15:21 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-22 15:19 [PATCH v5 00/11] mm: PMD-level swap entries for anonymous THPs Usama Arif
2026-07-22 15:19 ` Usama Arif [this message]
2026-07-22 15:19 ` [PATCH v5 02/11] mm: add PMD swap entry splitting support Usama Arif
2026-07-22 15:19 ` [PATCH v5 03/11] mm: handle PMD swap entries in fork path Usama Arif
2026-07-22 15:19 ` [PATCH v5 04/11] mm: zswap: add range lookup for large-folio swapin Usama Arif
2026-07-22 15:19 ` [PATCH v5 05/11] mm: swap in PMD swap entries as whole THPs during swapoff Usama Arif
2026-07-22 15:19 ` [PATCH v5 06/11] mm: handle PMD swap entries in non-present PMD walkers Usama Arif
2026-07-22 15:19 ` [PATCH v5 07/11] mm: handle PMD swap entries in MADV_WILLNEED Usama Arif
2026-07-22 15:19 ` [PATCH v5 08/11] mm: handle PMD swap entries in UFFDIO_MOVE Usama Arif
2026-07-22 15:19 ` [PATCH v5 09/11] mm: handle PMD swap entry faults on swap-in Usama Arif
2026-07-22 15:19 ` [PATCH v5 10/11] mm: install PMD swap entries on swap-out Usama Arif
2026-07-22 15:19 ` [PATCH v5 11/11] selftests/mm: add PMD swap entry tests Usama Arif
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