[PATCH v2 3/9] udf_rename(): only access the child content on cross-directory rename

From: Al Viro
Date: Sat Nov 25 2023 - 15:12:01 EST


We can't really afford locking the source on same-directory rename;
currently vfs_rename() tries to do that, but it will have to be
changed. The logics in udf_rename() is lazy and goes looking for
".." in source even in same-directory case. It's not hard to get
rid of that, leaving that behaviour only for cross-directory case;
that VFS can get locks safely (and will keep doing that after the
coming changes).

Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/udf/namei.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index 3508ac484da3..fac806a7a8d4 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -766,7 +766,7 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir,
struct inode *old_inode = d_inode(old_dentry);
struct inode *new_inode = d_inode(new_dentry);
struct udf_fileident_iter oiter, niter, diriter;
- bool has_diriter = false;
+ bool has_diriter = false, is_dir = false;
int retval;
struct kernel_lb_addr tloc;

@@ -789,6 +789,9 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir,
if (!empty_dir(new_inode))
goto out_oiter;
}
+ is_dir = true;
+ }
+ if (is_dir && old_dir != new_dir) {
retval = udf_fiiter_find_entry(old_inode, &dotdot_name,
&diriter);
if (retval == -ENOENT) {
@@ -878,7 +881,9 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir,
udf_dir_entry_len(&diriter.fi));
udf_fiiter_write_fi(&diriter, NULL);
udf_fiiter_release(&diriter);
+ }

+ if (is_dir) {
inode_dec_link_count(old_dir);
if (new_inode)
inode_dec_link_count(new_inode);
--
2.39.2