mm/readahead: Switch to page_cache_ra_order

do_page_cache_ra() was being exposed for the benefit of
do_sync_mmap_readahead().  Switch it over to page_cache_ra_order()
partly because it's a better interface but mostly for the benefit of
the next patch.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

mm/filemap.c

@@ -3027,7 +3027,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 	ra->size = ra->ra_pages;
 	ra->async_size = ra->ra_pages / 4;
 	ractl._index = ra->start;
-	do_page_cache_ra(&ractl, ra->size, ra->async_size);
+	page_cache_ra_order(&ractl, ra, 0);
 	return fpin;
 }
 

mm/internal.h

@@ -79,8 +79,8 @@ void unmap_page_range(struct mmu_gather *tlb,
 			     unsigned long addr, unsigned long end,
 			     struct zap_details *details);
 
-void do_page_cache_ra(struct readahead_control *, unsigned long nr_to_read,
-		unsigned long lookahead_size);
+void page_cache_ra_order(struct readahead_control *, struct file_ra_state *,
+		unsigned int order);
 void force_page_cache_ra(struct readahead_control *, unsigned long nr);
 static inline void force_page_cache_readahead(struct address_space *mapping,
 		struct file *file, pgoff_t index, unsigned long nr_to_read)

mm/readahead.c

@@ -247,7 +247,7 @@ EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
  * behaviour which would occur if page allocations are causing VM writeback.
  * We really don't want to intermingle reads and writes like that.
  */
-void do_page_cache_ra(struct readahead_control *ractl,
+static void do_page_cache_ra(struct readahead_control *ractl,
 		unsigned long nr_to_read, unsigned long lookahead_size)
 {
 	struct inode *inode = ractl->mapping->host;
@@ -462,7 +462,7 @@ static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index,
 	return err;
 }
 
-static void page_cache_ra_order(struct readahead_control *ractl,
+void page_cache_ra_order(struct readahead_control *ractl,
 		struct file_ra_state *ra, unsigned int new_order)
 {
 	struct address_space *mapping = ractl->mapping;