[PATCH 13/23] fuse: Convert fuse_write_begin() to use a folio

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

Fetch a folio from the page cache instead of a page and use it throughout
removing several calls to compound_head() and supporting large folios
(in this function).  We still have to convert back to a page for calling
internal fuse functions, but hopefully they will be converted soon.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/fuse/file.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f4102c6657af..137485999d3d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2391,41 +2391,42 @@ static int fuse_write_begin(struct file *file, struct address_space *mapping,
 {
 	pgoff_t index = pos >> PAGE_SHIFT;
 	struct fuse_conn *fc = get_fuse_conn(file_inode(file));
-	struct page *page;
+	struct folio *folio;
 	loff_t fsize;
 	int err = -ENOMEM;
 
 	WARN_ON(!fc->writeback_cache);
 
-	page = grab_cache_page_write_begin(mapping, index);
-	if (!page)
+	folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
+			mapping_gfp_mask(mapping));
+	if (IS_ERR(folio))
 		goto error;
 
-	fuse_wait_on_page_writeback(mapping->host, page->index);
+	fuse_wait_on_page_writeback(mapping->host, folio->index);
 
-	if (PageUptodate(page) || len == PAGE_SIZE)
+	if (folio_test_uptodate(folio) || len >= folio_size(folio))
 		goto success;
 	/*
-	 * Check if the start this page comes after the end of file, in which
-	 * case the readpage can be optimized away.
+	 * Check if the start of this folio comes after the end of file,
+	 * in which case the readpage can be optimized away.
 	 */
 	fsize = i_size_read(mapping->host);
-	if (fsize <= (pos & PAGE_MASK)) {
-		size_t off = pos & ~PAGE_MASK;
+	if (fsize <= folio_pos(folio)) {
+		size_t off = offset_in_folio(folio, pos);
 		if (off)
-			zero_user_segment(page, 0, off);
+			folio_zero_segment(folio, 0, off);
 		goto success;
 	}
-	err = fuse_do_readpage(file, page);
+	err = fuse_do_readpage(file, &folio->page);
 	if (err)
 		goto cleanup;
 success:
-	*pagep = page;
+	*pagep = &folio->page;
 	return 0;
 
 cleanup:
-	unlock_page(page);
-	put_page(page);
+	folio_unlock(folio);
+	folio_put(folio);
 error:
 	return err;
 }
-- 
2.43.0