fs: Introduce aops->read_folio

Change all the callers of ->readpage to call ->read_folio in preference,
if it exists.  This is a transitional duplication, and will be removed
by the end of the series.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/btrfs/file.c

@@ -2401,7 +2401,7 @@ static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
 {
 	struct address_space *mapping = filp->f_mapping;
 
-	if (!mapping->a_ops->readpage)
+	if (!mapping->a_ops->readpage && !mapping->a_ops->read_folio)
 		return -ENOEXEC;
 
 	file_accessed(filp);

fs/buffer.c

@@ -2824,7 +2824,10 @@ int nobh_truncate_page(struct address_space *mapping,
 
 	/* Ok, it's mapped. Make sure it's up-to-date */
 	if (!folio_test_uptodate(folio)) {
-		err = mapping->a_ops->readpage(NULL, &folio->page);
+		if (mapping->a_ops->read_folio)
+			err = mapping->a_ops->read_folio(NULL, folio);
+		else
+			err = mapping->a_ops->readpage(NULL, &folio->page);
 		if (err) {
 			folio_put(folio);
 			goto out;

fs/ceph/addr.c

@@ -1772,7 +1772,7 @@ int ceph_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct address_space *mapping = file->f_mapping;
 
-	if (!mapping->a_ops->readpage)
+	if (!mapping->a_ops->readpage && !mapping->a_ops->read_folio)
 		return -ENOEXEC;
 	file_accessed(file);
 	vma->vm_ops = &ceph_vmops;

include/linux/fs.h

@@ -336,6 +336,7 @@ static inline bool is_sync_kiocb(struct kiocb *kiocb)
 struct address_space_operations {
 	int (*writepage)(struct page *page, struct writeback_control *wbc);
 	int (*readpage)(struct file *, struct page *);
+	int (*read_folio)(struct file *, struct folio *);
 
 	/* Write back some dirty pages from this mapping. */
 	int (*writepages)(struct address_space *, struct writeback_control *);

kernel/events/uprobes.c

@@ -790,7 +790,7 @@ static int __copy_insn(struct address_space *mapping, struct file *filp,
 	 * and in page-cache. If ->readpage == NULL it must be shmem_mapping(),
 	 * see uprobe_register().
 	 */
-	if (mapping->a_ops->readpage)
+	if (mapping->a_ops->read_folio || mapping->a_ops->readpage)
 		page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp);
 	else
 		page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
@@ -1143,7 +1143,9 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 		return -EINVAL;
 
 	/* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
-	if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))
+	if (!inode->i_mapping->a_ops->read_folio &&
+	    !inode->i_mapping->a_ops->readpage &&
+	    !shmem_mapping(inode->i_mapping))
 		return -EIO;
 	/* Racy, just to catch the obvious mistakes */
 	if (offset > i_size_read(inode))

mm/filemap.c

@@ -2419,7 +2419,10 @@ static int filemap_read_folio(struct file *file, struct address_space *mapping,
 	 */
 	folio_clear_error(folio);
 	/* Start the actual read. The read will unlock the page. */
-	error = mapping->a_ops->readpage(file, &folio->page);
+	if (mapping->a_ops->read_folio)
+		error = mapping->a_ops->read_folio(file, folio);
+	else
+		error = mapping->a_ops->readpage(file, &folio->page);
 	if (error)
 		return error;
 
@@ -3447,7 +3450,7 @@ int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct address_space *mapping = file->f_mapping;
 
-	if (!mapping->a_ops->readpage)
+	if (!mapping->a_ops->read_folio && !mapping->a_ops->readpage)
 		return -ENOEXEC;
 	file_accessed(file);
 	vma->vm_ops = &generic_file_vm_ops;
@@ -3505,6 +3508,8 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
 filler:
 		if (filler)
 			err = filler(data, &folio->page);
+		else if (mapping->a_ops->read_folio)
+			err = mapping->a_ops->read_folio(data, folio);
 		else
 			err = mapping->a_ops->readpage(data, &folio->page);
 

mm/readahead.c

@@ -15,7 +15,7 @@
  * explicitly requested by the application.  Readahead only ever
  * attempts to read folios that are not yet in the page cache.  If a
  * folio is present but not up-to-date, readahead will not try to read
- * it. In that case a simple ->readpage() will be requested.
+ * it. In that case a simple ->read_folio() will be requested.
  *
  * Readahead is triggered when an application read request (whether a
  * system call or a page fault) finds that the requested folio is not in
@@ -78,7 +78,7 @@
  * address space operation, for which mpage_readahead() is a canonical
  * implementation.  ->readahead() should normally initiate reads on all
  * folios, but may fail to read any or all folios without causing an I/O
- * error.  The page cache reading code will issue a ->readpage() request
+ * error.  The page cache reading code will issue a ->read_folio() request
  * for any folio which ->readahead() did not read, and only an error
  * from this will be final.
  *
@@ -110,7 +110,7 @@
  * were not fetched with readahead_folio().  This will allow a
  * subsequent synchronous readahead request to try them again.  If they
  * are left in the page cache, then they will be read individually using
- * ->readpage() which may be less efficient.
+ * ->read_folio() which may be less efficient.
  */
 
 #include <linux/kernel.h>
@@ -170,8 +170,11 @@ static void read_pages(struct readahead_control *rac)
 			}
 			folio_unlock(folio);
 		}
+	} else if (aops->read_folio) {
+		while ((folio = readahead_folio(rac)) != NULL)
+			aops->read_folio(rac->file, folio);
 	} else {
-		while ((folio = readahead_folio(rac)))
+		while ((folio = readahead_folio(rac)) != NULL)
 			aops->readpage(rac->file, &folio->page);
 	}
 
@@ -302,7 +305,8 @@ void force_page_cache_ra(struct readahead_control *ractl,
 	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
 	unsigned long max_pages, index;
 
-	if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readahead))
+	if (unlikely(!mapping->a_ops->read_folio &&
+		     !mapping->a_ops->readpage && !mapping->a_ops->readahead))
 		return;
 
 	/*

mm/swapfile.c

@@ -3041,7 +3041,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	/*
 	 * Read the swap header.
 	 */
-	if (!mapping->a_ops->readpage) {
+	if (!mapping->a_ops->read_folio && !mapping->a_ops->readpage) {
 		error = -EINVAL;
 		goto bad_swap_unlock_inode;
 	}