ext4: convert to folio_create_empty_buffers

Remove an unnecessary folio->page->folio conversion and take advantage of
the new return value from folio_create_empty_buffers().

Link: https://lkml.kernel.org/r/20231016201114.1928083-5-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/ext4/inode.c

@@ -1020,10 +1020,8 @@ static int ext4_block_write_begin(struct folio *folio, loff_t pos, unsigned len,
 	BUG_ON(from > to);
 
 	head = folio_buffers(folio);
-	if (!head) {
-		create_empty_buffers(&folio->page, blocksize, 0);
-		head = folio_buffers(folio);
-	}
+	if (!head)
+		head = folio_create_empty_buffers(folio, blocksize, 0);
 	bbits = ilog2(blocksize);
 	block = (sector_t)folio->index << (PAGE_SHIFT - bbits);
 
@@ -1153,7 +1151,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
 	 * starting the handle.
 	 */
 	if (!folio_buffers(folio))
-		create_empty_buffers(&folio->page, inode->i_sb->s_blocksize, 0);
+		folio_create_empty_buffers(folio, inode->i_sb->s_blocksize, 0);
 
 	folio_unlock(folio);
 
@@ -3643,10 +3641,8 @@ static int __ext4_block_zero_page_range(handle_t *handle,
 	iblock = index << (PAGE_SHIFT - inode->i_sb->s_blocksize_bits);
 
 	bh = folio_buffers(folio);
-	if (!bh) {
-		create_empty_buffers(&folio->page, blocksize, 0);
-		bh = folio_buffers(folio);
-	}
+	if (!bh)
+		bh = folio_create_empty_buffers(folio, blocksize, 0);
 
 	/* Find the buffer that contains "offset" */
 	pos = blocksize;

fs/ext4/move_extent.c

@@ -183,10 +183,8 @@ mext_page_mkuptodate(struct folio *folio, unsigned from, unsigned to)
 
 	blocksize = i_blocksize(inode);
 	head = folio_buffers(folio);
-	if (!head) {
-		create_empty_buffers(&folio->page, blocksize, 0);
-		head = folio_buffers(folio);
-	}
+	if (!head)
+		head = folio_create_empty_buffers(folio, blocksize, 0);
 
 	block = (sector_t)folio->index << (PAGE_SHIFT - inode->i_blkbits);
 	for (bh = head, block_start = 0; bh != head || !block_start;
@@ -380,9 +378,10 @@ move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
 	}
 	/* Perform all necessary steps similar write_begin()/write_end()
 	 * but keeping in mind that i_size will not change */
-	if (!folio_buffers(folio[0]))
-		create_empty_buffers(&folio[0]->page, 1 << orig_inode->i_blkbits, 0);
 	bh = folio_buffers(folio[0]);
+	if (!bh)
+		bh = folio_create_empty_buffers(folio[0],
+				1 << orig_inode->i_blkbits, 0);
 	for (i = 0; i < data_offset_in_page; i++)
 		bh = bh->b_this_page;
 	for (i = 0; i < block_len_in_page; i++) {