[PATCH 7/9] sparc32: implement flush_anon_page

[Magnus Lindholm]

Generic GUP calls flush_anon_page() after pinning a page it is about to
reach through a kernel mapping. sparc32 never implemented it, so the user
alias can still hold dirty lines the kernel mapping cannot see.

The SMP wrapper checks whether the mm mask contains another CPU and then
uses the existing cross-call mechanism; it does not target exactly that
mask. HyperSPARC's unconditional all-CPU coverage is a separate fix.

The anonymous-page hook was introduced with a generic no-op fallback, and
SPARC32 has used that fallback since then. Supply the missing architecture
operation for the GUP coherency contract.

Fixes: 03beb07664d7 ("[PATCH] Add API for flushing Anon pages")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Magnus Lindholm <linmag7@xxxxxxxxx>
---
 arch/sparc/include/asm/cacheflush_32.h |  6 ++++++
 arch/sparc/mm/init_32.c                | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/sparc/include/asm/cacheflush_32.h b/arch/sparc/include/asm/cacheflush_32.h
index 9fee0ccfccb8..a65ee310e860 100644
--- a/arch/sparc/include/asm/cacheflush_32.h
+++ b/arch/sparc/include/asm/cacheflush_32.h
@@ -35,6 +35,12 @@
 #define flush_page_for_dma(addr) \
 	sparc32_cachetlb_ops->page_for_dma(addr)
 
+struct vm_area_struct;
+
+#define ARCH_HAS_FLUSH_ANON_PAGE
+void flush_anon_page(struct vm_area_struct *vma, struct page *page,
+		     unsigned long vaddr);
+
 void sparc_flush_page_to_ram(struct page *page);
 void sparc_flush_folio_to_ram(struct folio *folio);
 
diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
index 9cf0065fc2d4..d0ce9d23561e 100644
--- a/arch/sparc/mm/init_32.c
+++ b/arch/sparc/mm/init_32.c
@@ -95,6 +95,17 @@ void __init arch_mm_preinit(void)
 	}
 }
 
+/*
+ * Called after generic code pins an anon page it will reach through a kernel
+ * mapping; the user alias may hold dirty lines that mapping cannot see.
+ */
+void flush_anon_page(struct vm_area_struct *vma, struct page *page,
+		     unsigned long vaddr)
+{
+	if (PageAnon(page))
+		flush_cache_page(vma, vaddr, page_to_pfn(page));
+}
+
 void sparc_flush_page_to_ram(struct page *page)
 {
 	unsigned long vaddr = (unsigned long)page_address(page);
-- 
2.43.0