[PATCH 3.16 012/245] ext4: update c/mtime on truncate up

Ben Hutchings
2020-04-23T23:06:39Z

From: Eryu Guan <guaneryu@gmail.com>

commit 911af577de4e444622d46500c1f9a37ab4335d3a upstream.

Commit 3da40c7b0898 ("ext4: only call ext4_truncate when size <= isize")
introduced a bug that c/mtime is not updated on truncate up.

Fix the issue by setting c/mtime explicitly in the truncate up case.

Note that ftruncate(2) is not affected, so you won't see this bug using
truncate(1) and xfs_io(1).

Signed-off-by: Zirong Lang <zorro.lang@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext4/inode.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4843,6 +4843,14 @@ int ext4_setattr(struct dentry *dentry,
error = ext4_orphan_add(handle, inode);
orphan = 1;
}
+ /*
+ * Update c/mtime on truncate up, ext4_truncate() will
+ * update c/mtime in shrink case below
+ */
+ if (!shrink) {
+ inode->i_mtime = ext4_current_time(inode);
+ inode->i_ctime = inode->i_mtime;
+ }
down_write(&EXT4_I(inode)->i_data_sem);
EXT4_I(inode)->i_disksize = attr->ia_size;
rc = ext4_mark_inode_dirty(handle, inode);