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

[Tong Tiangen]

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