On Tue, Jul 26, 2016 at 12:02:13PM +0200, Miklos Szeredi wrote:
> On Mon, Jul 25, 2016 at 11:25 PM, Vito Caputo <vito.caputo@xxxxxxxxxx> wrote:
> > I think this strategy is an improvement, but I'm a bit apprehensive
> > about how specific it is to this particular style of untar-like
> > directory metadata preservation failure in only providing stability to
> > directory inode numbers.
> >
> > Additionally it introduces a userspace-visible mount option, for
> > something which /feels/ like a stop-gap kludge to make some things
> > work better in the short-term. Maybe it's acceptable, since a more
> > general solution could be implemented later which ignores the added
> > mount option without conflict.
Here's another patch that achieves stability without compromising
performance/disk usage.
Again not perfect, but perhaps good enough?
Thanks,
Miklos
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 12bcd07b9e32..5b7de7d489e0 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -143,13 +143,24 @@ static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getattr(&realpath, stat);
+ /*
+ * Use lower ino/dev for merged dir, so they are stable across copy up.
+ */
+ if (!err && OVL_TYPE_MERGE(type) && OVL_TYPE_UPPER(type)) {
+ struct path lowerpath;
+ struct kstat lowerstat;
+
+ ovl_path_lower(dentry, &lowerpath);
+ err = vfs_getattr(&lowerpath, &lowerstat);
+ if (!err) {
+ stat->dev = lowerstat.dev;
+ stat->ino = lowerstat.ino;
+ }
+ }
revert_creds(old_cred);
if (err)
return err;
- stat->dev = dentry->d_sb->s_dev;
- stat->ino = dentry->d_inode->i_ino;
-
/*
* It's probably not worth it to count subdirs to get the
* correct link count. nlink=1 seems to pacify 'find' and
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