mm/readahead: Convert page_cache_async_readahead to take a folio

Removes a couple of calls to compound_head and saves a few bytes.
Also convert verity's read_file_data_page() to be folio-based.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/btrfs/relocation.c

@@ -2967,8 +2967,9 @@ static int relocate_one_page(struct inode *inode, struct file_ra_state *ra,
 		goto release_page;
 
 	if (PageReadahead(page))
-		page_cache_async_readahead(inode->i_mapping, ra, NULL, page,
-				   page_index, last_index + 1 - page_index);
+		page_cache_async_readahead(inode->i_mapping, ra, NULL,
+				page_folio(page), page_index,
+				last_index + 1 - page_index);
 
 	if (!PageUptodate(page)) {
 		btrfs_readpage(NULL, page);

fs/btrfs/send.c

@@ -4986,7 +4986,8 @@ static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
 
 		if (PageReadahead(page)) {
 			page_cache_async_readahead(inode->i_mapping, &sctx->ra,
-				NULL, page, index, last_index + 1 - index);
+						NULL, page_folio(page), index,
+						last_index + 1 - index);
 		}
 
 		if (!PageUptodate(page)) {

fs/verity/enable.c

@@ -18,27 +18,26 @@
  * Read a file data page for Merkle tree construction.  Do aggressive readahead,
  * since we're sequentially reading the entire file.
  */
-static struct page *read_file_data_page(struct file *filp, pgoff_t index,
+static struct page *read_file_data_page(struct file *file, pgoff_t index,
 					struct file_ra_state *ra,
 					unsigned long remaining_pages)
 {
-	struct page *page;
+	DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, index);
+	struct folio *folio;
 
-	page = find_get_page_flags(filp->f_mapping, index, FGP_ACCESSED);
-	if (!page || !PageUptodate(page)) {
-		if (page)
-			put_page(page);
+	folio = __filemap_get_folio(ractl.mapping, index, FGP_ACCESSED, 0);
+	if (!folio || !folio_test_uptodate(folio)) {
+		if (folio)
+			folio_put(folio);
 		else
-			page_cache_sync_readahead(filp->f_mapping, ra, filp,
-						  index, remaining_pages);
-		page = read_mapping_page(filp->f_mapping, index, NULL);
-		if (IS_ERR(page))
-			return page;
+			page_cache_sync_ra(&ractl, remaining_pages);
+		folio = read_cache_folio(ractl.mapping, index, NULL, file);
+		if (IS_ERR(folio))
+			return &folio->page;
 	}
-	if (PageReadahead(page))
-		page_cache_async_readahead(filp->f_mapping, ra, filp, page,
-					   index, remaining_pages);
-	return page;
+	if (folio_test_readahead(folio))
+		page_cache_async_ra(&ractl, folio, remaining_pages);
+	return folio_file_page(folio, index);
 }
 
 static int build_merkle_tree_level(struct file *filp, unsigned int level,

include/linux/pagemap.h

@@ -1242,7 +1242,7 @@ void page_cache_sync_readahead(struct address_space *mapping,
  * @mapping: address_space which holds the pagecache and I/O vectors
  * @ra: file_ra_state which holds the readahead state
  * @file: Used by the filesystem for authentication.
- * @page: The page at @index which triggered the readahead call.
+ * @folio: The folio at @index which triggered the readahead call.
  * @index: Index of first page to be read.
  * @req_count: Total number of pages being read by the caller.
  *
@@ -1254,10 +1254,10 @@ void page_cache_sync_readahead(struct address_space *mapping,
 static inline
 void page_cache_async_readahead(struct address_space *mapping,
 		struct file_ra_state *ra, struct file *file,
-		struct page *page, pgoff_t index, unsigned long req_count)
+		struct folio *folio, pgoff_t index, unsigned long req_count)
 {
 	DEFINE_READAHEAD(ractl, file, ra, mapping, index);
-	page_cache_async_ra(&ractl, page_folio(page), req_count);
+	page_cache_async_ra(&ractl, folio, req_count);
 }
 
 static inline struct folio *__readahead_folio(struct readahead_control *ractl)