[PATCH -next 1/2] riscv/mm: hugepage's PG_dcache_clean flag is only set in head page

From: Tong Tiangen
Date: Mon Oct 24 2022 - 05:21:57 EST


HugeTLB pages are always fully mapped, so only setting head page's
PG_dcache_clean flag is enough.

This refers to the following link:
https://lore.kernel.org/lkml/20220331065640.5777-2-songmuchun@xxxxxxxxxxxxx/

Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
---
arch/riscv/include/asm/cacheflush.h | 7 +++++++
arch/riscv/mm/cacheflush.c | 7 +++++++
2 files changed, 14 insertions(+)

diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index 8a5c246b0a21..c172d05de474 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -17,6 +17,13 @@ static inline void local_flush_icache_all(void)

static inline void flush_dcache_page(struct page *page)
{
+ /*
+ * HugeTLB pages are always fully mapped and only head page will be
+ * set PG_dcache_clean (see comments in flush_icache_pte()).
+ */
+ if (PageHuge(page))
+ page = compound_head(page);
+
if (test_bit(PG_dcache_clean, &page->flags))
clear_bit(PG_dcache_clean, &page->flags);
}
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 6cb7d96ad9c7..062559c04fc3 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -82,6 +82,13 @@ void flush_icache_pte(pte_t pte)
{
struct page *page = pte_page(pte);

+ /*
+ * HugeTLB pages are always fully mapped, so only setting head page's
+ * PG_dcache_clean flag is enough.
+ */
+ if (PageHuge(page))
+ page = compound_head(page);
+
if (!test_and_set_bit(PG_dcache_clean, &page->flags))
flush_icache_all();
}
--
2.25.1