On 03.06.25 23:16, David Hildenbrand wrote:
Marking PUDs that map a "normal" refcounted folios as special is
against our rules documented for vm_normal_page().
Fortunately, there are not that many pud_special() check that can be
mislead and are right now rather harmless: e.g., none so far
bases decisions whether to grab a folio reference on that decision.
Well, and GUP-fast will fallback to GUP-slow. All in all, so far no big
implications as it seems.
Getting this right will get more important as we introduce
folio_normal_page_pud() and start using it in more place where we
currently special-case based on other VMA flags.
Fix it by just inlining the relevant code, making the whole
pud_none() handling cleaner.
Add folio_mk_pud() to mimic what we do with folio_mk_pmd().
While at it, make sure that the pud that is non-none is actually present
before comparing PFNs.
Fixes: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()")
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
include/linux/mm.h | 15 +++++++++++++++
mm/huge_memory.c | 33 +++++++++++++++++++++++----------
2 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0ef2ba0c667af..047c8261d4002 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1816,6 +1816,21 @@ static inline pmd_t folio_mk_pmd(struct folio *folio,
pgprot_t pgprot)
{
return pmd_mkhuge(pfn_pmd(folio_pfn(folio), pgprot));
}
+
+/**
+ * folio_mk_pud - Create a PUD for this folio
+ * @folio: The folio to create a PUD for
+ * @pgprot: The page protection bits to use
+ *
+ * Create a page table entry for the first page of this folio.
+ * This is suitable for passing to set_pud_at().
+ *
+ * Return: A page table entry suitable for mapping this folio.
+ */
+static inline pud_t folio_mk_pud(struct folio *folio, pgprot_t pgprot)
+{
+ return pud_mkhuge(pfn_pud(folio_pfn(folio), pgprot));
+}
#endif
#endif /* CONFIG_MMU */
The following on top should make cross-compiles happy (git diff output because
it's late
here, probably whitespace messed up):
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 047c8261d4002..b7e2abd8ce0df 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1817,6 +1817,7 @@ static inline pmd_t folio_mk_pmd(struct folio *folio,
pgprot_t pgprot)
return pmd_mkhuge(pfn_pmd(folio_pfn(folio), pgprot));
}
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
/**
* folio_mk_pud - Create a PUD for this folio
* @folio: The folio to create a PUD for
@@ -1831,7 +1832,8 @@ static inline pud_t folio_mk_pud(struct folio *folio,
pgprot_t pgprot)
{
return pud_mkhuge(pfn_pud(folio_pfn(folio), pgprot));
}
-#endif
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif /* CONFIG_MMU */
static inline bool folio_has_pincount(const struct folio *folio
--
Cheers,
David / dhildenb
