[PATCH 2/2] hfs: remove the dead grow path from hfs_file_truncate()

[Hengyu Liang]

hfs_file_truncate() grows the file through hfs_write_begin() when
i_size is larger than phys_size. That case no longer happens.

phys_size is set to i_size when the inode is read. After that, i_size
only grows through hfs_write_begin(), which grows phys_size first, or
through a direct write that ends within phys_size.
"hfs: report errors when extending files with setattr" made
hfs_inode_setattr() extend files with generic_cont_expand_simple(),
and "hfs: fall back to buffered I/O for direct writes past phys_size"
made direct writes past phys_size go through hfs_write_begin() too.

This patch removes the grow path, and warns and returns if i_size is
ever larger than phys_size.

Suggested-by: Viacheslav Dubeyko <slava@xxxxxxxxxxx>
Signed-off-by: Hengyu Liang <hengyul@xxxxxxxxxx>
---
 fs/hfs/extent.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/fs/hfs/extent.c b/fs/hfs/extent.c
index 26357086517f..8d04b7c0911e 100644
--- a/fs/hfs/extent.c
+++ b/fs/hfs/extent.c
@@ -491,23 +491,9 @@ void hfs_file_truncate(struct inode *inode)
 	hfs_dbg("ino %llu, phys_size %llu -> i_size %llu\n",
 		inode->i_ino, (long long)HFS_I(inode)->phys_size,
 		inode->i_size);
-	if (inode->i_size > HFS_I(inode)->phys_size) {
-		struct address_space *mapping = inode->i_mapping;
-		void *fsdata = NULL;
-		struct folio *folio;
-
-		/* XXX: Can use generic_cont_expand? */
-		size = inode->i_size - 1;
-		res = hfs_write_begin(NULL, mapping, size + 1, 0, &folio,
-				&fsdata);
-		if (!res) {
-			res = generic_write_end(NULL, mapping, size + 1, 0, 0,
-					folio, fsdata);
-		}
-		if (res)
-			inode->i_size = HFS_I(inode)->phys_size;
+	if (WARN_ON_ONCE(inode->i_size > HFS_I(inode)->phys_size))
 		return;
-	} else if (inode->i_size == HFS_I(inode)->phys_size)
+	if (inode->i_size == HFS_I(inode)->phys_size)
 		return;
 	size = inode->i_size + HFS_SB(sb)->alloc_blksz - 1;
 	blk_cnt = size / HFS_SB(sb)->alloc_blksz;
-- 
2.53.0