mm: convert pagecache_isize_extended to use a folio

JIRA: https://issues.redhat.com/browse/RHEL-109217

commit 2ebe90d
Author: Matthew Wilcox (Oracle) <willy@infradead.org>
Date:   Fri Apr 5 19:00:36 2024 +0100

    mm: convert pagecache_isize_extended to use a folio

    Remove four hidden calls to compound_head().  Also exit early if the
    filesystem block size is >= PAGE_SIZE instead of just equal to PAGE_SIZE.

    Link: https://lkml.kernel.org/r/20240405180038.2618624-1-willy@infradead.org
    Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
    Reviewed-by: David Hildenbrand <david@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Brian Foster <bfoster@redhat.com>

Author: Brian Foster

mm/truncate.c

@@ -766,15 +766,15 @@ EXPORT_SYMBOL(truncate_setsize);
  * @from:	original inode size
  * @to:		new inode size
  *
- * Handle extension of inode size either caused by extending truncate or by
- * write starting after current i_size. We mark the page straddling current
- * i_size RO so that page_mkwrite() is called on the nearest write access to
- * the page.  This way filesystem can be sure that page_mkwrite() is called on
- * the page before user writes to the page via mmap after the i_size has been
- * changed.
+ * Handle extension of inode size either caused by extending truncate or
+ * by write starting after current i_size.  We mark the page straddling
+ * current i_size RO so that page_mkwrite() is called on the first
+ * write access to the page.  The filesystem will update its per-block
+ * information before user writes to the page via mmap after the i_size
+ * has been changed.
  *
  * The function must be called after i_size is updated so that page fault
- * coming after we unlock the page will already see the new i_size.
+ * coming after we unlock the folio will already see the new i_size.
  * The function must be called while we still hold i_rwsem - this not only
  * makes sure i_size is stable but also that userspace cannot observe new
  * i_size value before we are prepared to store mmap writes at new inode size.
@@ -783,31 +783,29 @@ void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
 {
 	int bsize = i_blocksize(inode);
 	loff_t rounded_from;
-	struct page *page;
-	pgoff_t index;
+	struct folio *folio;
 
 	WARN_ON(to > inode->i_size);
 
-	if (from >= to || bsize == PAGE_SIZE)
+	if (from >= to || bsize >= PAGE_SIZE)
 		return;
 	/* Page straddling @from will not have any hole block created? */
 	rounded_from = round_up(from, bsize);
 	if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
 		return;
 
-	index = from >> PAGE_SHIFT;
-	page = find_lock_page(inode->i_mapping, index);
-	/* Page not cached? Nothing to do */
-	if (!page)
+	folio = filemap_lock_folio(inode->i_mapping, from / PAGE_SIZE);
+	/* Folio not cached? Nothing to do */
+	if (IS_ERR(folio))
 		return;
 	/*
-	 * See clear_page_dirty_for_io() for details why set_page_dirty()
+	 * See folio_clear_dirty_for_io() for details why folio_mark_dirty()
 	 * is needed.
 	 */
-	if (page_mkclean(page))
-		set_page_dirty(page);
-	unlock_page(page);
-	put_page(page);
+	if (folio_mkclean(folio))
+		folio_mark_dirty(folio);
+	folio_unlock(folio);
+	folio_put(folio);
 }
 EXPORT_SYMBOL(pagecache_isize_extended);