ovl: constant d_ino for non-merge dirs

Impure directories are ones which contain objects with origins (i.e. those
that have been copied up).  These are relevant to readdir operation only
because of the d_ino field, no other transformation is necessary.  Also a
directory can become impure between two getdents(2) calls.

This patch creates a cache for impure directories.  Unlike the cache for
merged directories, this one only contains entries with origin and is not
refcounted but has a its lifetime tied to that of the dentry.

Similarly to the merged cache, the impure cache is invalidated based on a
version number.  This version number is incremented when an entry with
origin is added or removed from the directory.

If the cache is empty, then the impure xattr is removed from the directory.

This patch also fixes up handling of d_ino for the ".." entry if the parent
directory is merged.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/dir.c

@@ -155,7 +155,7 @@ static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
 static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
 			    struct dentry *newdentry, bool hardlink)
 {
-	ovl_dentry_version_inc(dentry->d_parent);
+	ovl_dentry_version_inc(dentry->d_parent, false);
 	ovl_dentry_set_upper_alias(dentry);
 	if (!hardlink) {
 		ovl_inode_update(inode, newdentry);
@@ -692,7 +692,7 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 	if (flags)
 		ovl_cleanup(wdir, upper);
 
-	ovl_dentry_version_inc(dentry->d_parent);
+	ovl_dentry_version_inc(dentry->d_parent, true);
 out_d_drop:
 	d_drop(dentry);
 	dput(whiteout);
@@ -742,7 +742,7 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 		err = vfs_rmdir(dir, upper);
 	else
 		err = vfs_unlink(dir, upper, NULL);
-	ovl_dentry_version_inc(dentry->d_parent);
+	ovl_dentry_version_inc(dentry->d_parent, ovl_type_origin(dentry));
 
 	/*
 	 * Keeping this dentry hashed would mean having to release
@@ -1089,8 +1089,9 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 			drop_nlink(d_inode(new));
 	}
 
-	ovl_dentry_version_inc(old->d_parent);
-	ovl_dentry_version_inc(new->d_parent);
+	ovl_dentry_version_inc(old->d_parent,
+			       !overwrite && ovl_type_origin(new));
+	ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old));
 
 out_dput:
 	dput(newdentry);

fs/overlayfs/overlayfs.h

@@ -204,8 +204,8 @@ struct dentry *ovl_i_dentry_upper(struct inode *inode);
 struct inode *ovl_inode_upper(struct inode *inode);
 struct inode *ovl_inode_lower(struct inode *inode);
 struct inode *ovl_inode_real(struct inode *inode);
-struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry);
-void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache);
+struct ovl_dir_cache *ovl_dir_cache(struct inode *inode);
+void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache);
 bool ovl_dentry_is_opaque(struct dentry *dentry);
 bool ovl_dentry_is_whiteout(struct dentry *dentry);
 void ovl_dentry_set_opaque(struct dentry *dentry);
@@ -217,7 +217,7 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect);
 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 		    struct dentry *lowerdentry);
 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry);
-void ovl_dentry_version_inc(struct dentry *dentry);
+void ovl_dentry_version_inc(struct dentry *dentry, bool impurity);
 u64 ovl_dentry_version_get(struct dentry *dentry);
 bool ovl_is_whiteout(struct dentry *dentry);
 struct file *ovl_path_open(struct path *path, int flags);
@@ -229,6 +229,7 @@ int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
 		       int xerr);
 int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry);
 void ovl_set_flag(unsigned long flag, struct inode *inode);
+void ovl_clear_flag(unsigned long flag, struct inode *inode);
 bool ovl_test_flag(unsigned long flag, struct inode *inode);
 bool ovl_inuse_trylock(struct dentry *dentry);
 void ovl_inuse_unlock(struct dentry *dentry);
@@ -256,6 +257,7 @@ extern const struct file_operations ovl_dir_operations;
 int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list);
 void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list);
 void ovl_cache_free(struct list_head *list);
+void ovl_dir_cache_free(struct inode *inode);
 int ovl_check_d_type_supported(struct path *realpath);
 void ovl_workdir_cleanup(struct inode *dir, struct vfsmount *mnt,
 			 struct dentry *dentry, int level);

fs/overlayfs/super.c

@@ -198,6 +198,7 @@ static void ovl_destroy_inode(struct inode *inode)
 
 	dput(oi->__upperdentry);
 	kfree(oi->redirect);
+	ovl_dir_cache_free(inode);
 	mutex_destroy(&oi->lock);
 
 	call_rcu(&inode->i_rcu, ovl_i_callback);

fs/overlayfs/util.c

@@ -180,14 +180,14 @@ struct inode *ovl_inode_real(struct inode *inode)
 }
 
 
-struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
+struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
 {
-	return OVL_I(d_inode(dentry))->cache;
+	return OVL_I(inode)->cache;
 }
 
-void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
+void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
 {
-	OVL_I(d_inode(dentry))->cache = cache;
+	OVL_I(inode)->cache = cache;
 }
 
 bool ovl_dentry_is_opaque(struct dentry *dentry)
@@ -275,12 +275,19 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
 	}
 }
 
-void ovl_dentry_version_inc(struct dentry *dentry)
+void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
 {
 	struct inode *inode = d_inode(dentry);
 
 	WARN_ON(!inode_is_locked(inode));
-	OVL_I(inode)->version++;
+	/*
+	 * Version is used by readdir code to keep cache consistent.  For merge
+	 * dirs all changes need to be noted.  For non-merge dirs, cache only
+	 * contains impure (ones which have been copied up and have origins)
+	 * entries, so only need to note changes to impure entries.
+	 */
+	if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
+		OVL_I(inode)->version++;
 }
 
 u64 ovl_dentry_version_get(struct dentry *dentry)
@@ -382,6 +389,11 @@ void ovl_set_flag(unsigned long flag, struct inode *inode)
 	set_bit(flag, &OVL_I(inode)->flags);
 }
 
+void ovl_clear_flag(unsigned long flag, struct inode *inode)
+{
+	clear_bit(flag, &OVL_I(inode)->flags);
+}
+
 bool ovl_test_flag(unsigned long flag, struct inode *inode)
 {
 	return test_bit(flag, &OVL_I(inode)->flags);