On Mon, Mar 23, 2020 at 3:21 PM Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>
> On Mon, Mar 23, 2020 at 2:24 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> > IDGI. coming from vfs_unlink() and vfs_rename() it doesn't look like
> > it is possible for victim inode not to have a hashed alias, so the
> > alias test seems futile.
>
> Yeah, needs a comment: both ovl_remove_upper() and
> ovl_remove_and_whiteout() unhash the dentry before returning, so
> d_find_alias() will find another hashed dentry or none.
Except that doesn't seem to be true for the overwriting rename case...
Attached patch should work for both.
Thanks,
Miklos
---
fs/overlayfs/dir.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -819,6 +819,27 @@ static bool ovl_pure_upper(struct dentry
!ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
}
+static void ovl_drop_nlink(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ struct dentry *alias;
+
+ spin_lock(&inode->i_lock);
+ hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
+ if (alias != dentry && !d_unhashed(alias))
+ break;
+ }
+ spin_unlock(&inode->i_lock);
+
+ /*
+ * Changes to underlying layers may cause i_nlink to lose sync with
+ * reality. In this case prevent the link count from going to zero
+ * prematurely.
+ */
+ if (inode->i_nlink > !!alias)
+ drop_nlink(inode);
+}
+
static int ovl_do_remove(struct dentry *dentry, bool is_dir)
{
int err;
@@ -856,7 +877,7 @@ static int ovl_do_remove(struct dentry *
if (is_dir)
clear_nlink(dentry->d_inode);
else
- drop_nlink(dentry->d_inode);
+ ovl_drop_nlink(dentry);
}
ovl_nlink_end(dentry);
@@ -1201,7 +1222,7 @@ static int ovl_rename(struct inode *oldd
if (new_is_dir)
clear_nlink(d_inode(new));
else
- drop_nlink(d_inode(new));
+ ovl_drop_nlink(new);
}
ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
