freevxfs: Convert vxfs_immed_read_folio() to use a folio

Reorganise the file to remove the forward declaration.
Use folios throughout vxfs_immed_read_folio().
Use memcpy_to_page() instead of an open-coded kmap()/kunmap().
Remove flush_dcache_page() as this is embedded in memcpy_to_page().
Use folio_pos() instead of opencoding it.
Handle multi-page folios.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/freevxfs/vxfs_immed.c

@@ -13,16 +13,6 @@
 #include "vxfs_extern.h"
 #include "vxfs_inode.h"
 
-
-static int	vxfs_immed_read_folio(struct file *, struct folio *);
-
-/*
- * Address space operations for immed files and directories.
- */
-const struct address_space_operations vxfs_immed_aops = {
-	.read_folio =		vxfs_immed_read_folio,
-};
-
 /**
  * vxfs_immed_read_folio - read part of an immed inode into pagecache
  * @file:	file context (unused)
@@ -30,7 +20,7 @@ const struct address_space_operations vxfs_immed_aops = {
  *
  * Description:
  *   vxfs_immed_read_folio reads a part of the immed area of the
- *   file that hosts @pp into the pagecache.
+ *   file that hosts @folio into the pagecache.
  *
  * Returns:
  *   Zero on success, else a negative error code.
@@ -38,21 +28,26 @@ const struct address_space_operations vxfs_immed_aops = {
  * Locking status:
  *   @folio is locked and will be unlocked.
  */
-static int
-vxfs_immed_read_folio(struct file *fp, struct folio *folio)
+static int vxfs_immed_read_folio(struct file *fp, struct folio *folio)
 {
-	struct page *pp = &folio->page;
-	struct vxfs_inode_info	*vip = VXFS_INO(pp->mapping->host);
-	u_int64_t	offset = (u_int64_t)pp->index << PAGE_SHIFT;
-	caddr_t		kaddr;
+	struct vxfs_inode_info *vip = VXFS_INO(folio->mapping->host);
+	void *src = vip->vii_immed.vi_immed + folio_pos(folio);
+	unsigned long i;
 
-	kaddr = kmap(pp);
-	memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);
-	kunmap(pp);
-	
-	flush_dcache_page(pp);
-	SetPageUptodate(pp);
-        unlock_page(pp);
+	for (i = 0; i < folio_nr_pages(folio); i++) {
+		memcpy_to_page(folio_page(folio, i), 0, src, PAGE_SIZE);
+		src += PAGE_SIZE;
+	}
+
+	folio_mark_uptodate(folio);
+	folio_unlock(folio);
 
 	return 0;
 }
+
+/*
+ * Address space operations for immed files and directories.
+ */
+const struct address_space_operations vxfs_immed_aops = {
+	.read_folio =	vxfs_immed_read_folio,
+};