Subject: [PATCH 07/10] ext2: Handle large block size directories in ext2_delete_entry()

From: "Matthew Wilcox (Oracle)" <[email-masked]>
Date: Thu, 21 Sep 2023 14:50:36 -0400

If the block size is > PAGE_SIZE, we need to calculate these offsets
relative to the start of the folio, not the page.

Signed-off-by: Matthew Wilcox (Oracle) <[email-masked]>
---
 fs/ext2/dir.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 2fc910e99234..7e75cfaa709c 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -586,16 +586,20 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
  */
 int ext2_delete_entry(struct ext2_dir_entry_2 *dir, struct page *page)
 {
-	struct inode *inode = page->mapping->host;
-	char *kaddr = (char *)((unsigned long)dir & PAGE_MASK);
-	unsigned from = offset_in_page(dir) & ~(ext2_chunk_size(inode)-1);
-	unsigned to = offset_in_page(dir) +
-				ext2_rec_len_from_disk(dir->rec_len);
+	struct folio *folio = page_folio(page);
+	struct inode *inode = folio->mapping->host;
+	size_t from, to;
+	char *kaddr;
 	loff_t pos;
-	ext2_dirent *pde = NULL;
-	ext2_dirent *de = (ext2_dirent *)(kaddr + from);
+	ext2_dirent *de, *pde = NULL;
 	int err;
 
+	from = offset_in_folio(folio, dir);
+	to = from + ext2_rec_len_from_disk(dir->rec_len);
+	kaddr = (char *)dir - from;
+	from &= ~(ext2_chunk_size(inode)-1);
+	de = (ext2_dirent *)(kaddr + from);
+
 	while ((char*)de < (char*)dir) {
 		if (de->rec_len == 0) {
 			ext2_error(inode->i_sb, __func__,
@@ -606,18 +610,18 @@ int ext2_delete_entry(struct ext2_dir_entry_2 *dir, struct page *page)
 		de = ext2_next_entry(de);
 	}
 	if (pde)
-		from = offset_in_page(pde);
-	pos = page_offset(page) + from;
-	lock_page(page);
-	err = ext2_prepare_chunk(page, pos, to - from);
+		from = offset_in_folio(folio, pde);
+	pos = folio_pos(folio) + from;
+	folio_lock(folio);
+	err = ext2_prepare_chunk(&folio->page, pos, to - from);
 	if (err) {
-		unlock_page(page);
+		folio_unlock(folio);
 		return err;
 	}
 	if (pde)
 		pde->rec_len = ext2_rec_len_to_disk(to - from);
 	dir->inode = 0;
-	ext2_commit_chunk(page, pos, to - from);
+	ext2_commit_chunk(&folio->page, pos, to - from);
 	inode->i_mtime = inode_set_ctime_current(inode);
 	EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
 	mark_inode_dirty(inode);
-- 
2.40.1