mm: Add flush_dcache_folio()

This is a default implementation which calls flush_dcache_page() on
each page in the folio. If architectures can do better, they should
implement their own version of it.

Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>

Documentation/core-api/cachetlb.rst

···
 			dirty.  Again, see sparc64 for examples of how
 			to deal with this.
 
+  ``void flush_dcache_folio(struct folio *folio)``
+	This function is called under the same circumstances as
+	flush_dcache_page().  It allows the architecture to
+	optimise for flushing the entire folio of pages instead
+	of flushing one page at a time.
+
   ``void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
   unsigned long user_vaddr, void *dst, void *src, int len)``
   ``void copy_from_user_page(struct vm_area_struct *vma, struct page *page,

arch/arc/include/asm/cacheflush.h

···
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
 
 void flush_dcache_page(struct page *page);
+void flush_dcache_folio(struct folio *folio);
 
 void dma_cache_wback_inv(phys_addr_t start, unsigned long sz);
 void dma_cache_inv(phys_addr_t start, unsigned long sz);

arch/arm/include/asm/cacheflush.h

···
  */
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
 extern void flush_dcache_page(struct page *);
+void flush_dcache_folio(struct folio *folio);
 
 #define ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE 1
 static inline void flush_kernel_vmap_range(void *addr, int size)

arch/m68k/include/asm/cacheflush_mm.h

···
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
 #define flush_dcache_page(page)		__flush_page_to_ram(page_address(page))
+void flush_dcache_folio(struct folio *folio);
 #define flush_dcache_mmap_lock(mapping)		do { } while (0)
 #define flush_dcache_mmap_unlock(mapping)	do { } while (0)
 #define flush_icache_page(vma, page)	__flush_page_to_ram(page_address(page))

arch/mips/include/asm/cacheflush.h

···
 		SetPageDcacheDirty(page);
 }
 
+void flush_dcache_folio(struct folio *folio);
+
 #define flush_dcache_mmap_lock(mapping)		do { } while (0)
 #define flush_dcache_mmap_unlock(mapping)	do { } while (0)
 

arch/nds32/include/asm/cacheflush.h

···
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
 void flush_dcache_page(struct page *page);
+void flush_dcache_folio(struct folio *folio);
 void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 		       unsigned long vaddr, void *dst, void *src, int len);
 void copy_from_user_page(struct vm_area_struct *vma, struct page *page,

arch/nios2/include/asm/cacheflush.h

···
 extern void flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr,
 	unsigned long pfn);
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
-extern void flush_dcache_page(struct page *page);
+void flush_dcache_page(struct page *page);
+void flush_dcache_folio(struct folio *folio);
 
 extern void flush_icache_range(unsigned long start, unsigned long end);
 extern void flush_icache_page(struct vm_area_struct *vma, struct page *page);

arch/parisc/include/asm/cacheflush.h

···
 #define flush_cache_vunmap(start, end)		flush_cache_all()
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
-extern void flush_dcache_page(struct page *page);
+void flush_dcache_page(struct page *page);
+void flush_dcache_folio(struct folio *folio);
 
 #define flush_dcache_mmap_lock(mapping)		xa_lock_irq(&mapping->i_pages)
 #define flush_dcache_mmap_unlock(mapping)	xa_unlock_irq(&mapping->i_pages)

arch/sh/include/asm/cacheflush.h

···
 extern void flush_cache_range(struct vm_area_struct *vma,
 				 unsigned long start, unsigned long end);
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
-extern void flush_dcache_page(struct page *page);
+void flush_dcache_page(struct page *page);
+void flush_dcache_folio(struct folio *folio);
 extern void flush_icache_range(unsigned long start, unsigned long end);
 #define flush_icache_user_range flush_icache_range
 extern void flush_icache_page(struct vm_area_struct *vma,

arch/xtensa/include/asm/cacheflush.h

···
 #define flush_cache_vunmap(start,end)	flush_cache_all()
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
-extern void flush_dcache_page(struct page*);
+void flush_dcache_page(struct page *);
+void flush_dcache_folio(struct folio *);
 
 void local_flush_cache_range(struct vm_area_struct *vma,
 		unsigned long start, unsigned long end);
···
 #define flush_cache_vunmap(start,end)			do { } while (0)
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
+#define ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
 #define flush_dcache_page(page)				do { } while (0)
+static inline void flush_dcache_folio(struct folio *folio) { }
 
 #define flush_icache_range local_flush_icache_range
 #define flush_cache_page(vma, addr, pfn)		do { } while (0)

include/asm-generic/cacheflush.h

···
 static inline void flush_dcache_page(struct page *page)
 {
 }
+
+static inline void flush_dcache_folio(struct folio *folio) { }
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
+#define ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
 #endif
 
+#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
+void flush_dcache_folio(struct folio *folio);
+#endif
 
 #ifndef flush_dcache_mmap_lock
 static inline void flush_dcache_mmap_lock(struct address_space *mapping)

mm/util.c

···
 	up_write(&page_offline_rwsem);
 }
 EXPORT_SYMBOL(page_offline_end);
+
+#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_FOLIO
+void flush_dcache_folio(struct folio *folio)
+{
+	long i, nr = folio_nr_pages(folio);
+
+	for (i = 0; i < nr; i++)
+		flush_dcache_page(folio_page(folio, i));
+}
+EXPORT_SYMBOL(flush_dcache_folio);
+#endif