ovl: use ovl_inode mutex to synchronize concurrent copy up

Use the new ovl_inode mutex to synchonize concurrent copy up
instead of the super block copy up workqueue.

Moving the synchronization object from the overlay dentry to
the overlay inode is needed for synchonizing concurrent copy up
of lower hardlinks to the same upper inode.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/ovl_entry.h

@@ -29,7 +29,6 @@ struct ovl_fs {
 	const struct cred *creator_cred;
 	bool tmpfile;
 	bool noxattr;
-	wait_queue_head_t copyup_wq;
 	/* sb common to all layers */
 	struct super_block *same_sb;
 };
@@ -41,7 +40,6 @@ struct ovl_entry {
 		struct {
 			u64 version;
 			bool opaque;
-			bool copying;
 		};
 		struct rcu_head rcu;
 	};
@@ -57,6 +55,9 @@ struct ovl_inode {
 	struct inode vfs_inode;
 	struct dentry *__upperdentry;
 	struct inode *lower;
+
+	/* synchronize copy up and more */
+	struct mutex lock;
 };
 
 static inline struct ovl_inode *OVL_I(struct inode *inode)

fs/overlayfs/super.c

@@ -173,6 +173,7 @@ static struct inode *ovl_alloc_inode(struct super_block *sb)
 	oi->flags = 0;
 	oi->__upperdentry = NULL;
 	oi->lower = NULL;
+	mutex_init(&oi->lock);
 
 	return &oi->vfs_inode;
 }
@@ -190,6 +191,7 @@ static void ovl_destroy_inode(struct inode *inode)
 
 	dput(oi->__upperdentry);
 	kfree(oi->redirect);
+	mutex_destroy(&oi->lock);
 
 	call_rcu(&inode->i_rcu, ovl_i_callback);
 }
@@ -782,7 +784,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	if (!ufs)
 		goto out;
 
-	init_waitqueue_head(&ufs->copyup_wq);
 	ufs->config.redirect_dir = ovl_redirect_dir_def;
 	err = ovl_parse_opt((char *) data, &ufs->config);
 	if (err)

fs/overlayfs/util.c

@@ -270,32 +270,21 @@ struct file *ovl_path_open(struct path *path, int flags)
 
 int ovl_copy_up_start(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	struct ovl_entry *oe = dentry->d_fsdata;
+	struct ovl_inode *oi = OVL_I(d_inode(dentry));
 	int err;
 
-	spin_lock(&ofs->copyup_wq.lock);
-	err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
-	if (!err) {
-		if (ovl_dentry_upper(dentry))
-			err = 1; /* Already copied up */
-		else
-			oe->copying = true;
+	err = mutex_lock_interruptible(&oi->lock);
+	if (!err && ovl_dentry_upper(dentry)) {
+		err = 1; /* Already copied up */
+		mutex_unlock(&oi->lock);
 	}
-	spin_unlock(&ofs->copyup_wq.lock);
 
 	return err;
 }
 
 void ovl_copy_up_end(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
-	struct ovl_entry *oe = dentry->d_fsdata;
-
-	spin_lock(&ofs->copyup_wq.lock);
-	oe->copying = false;
-	wake_up_locked(&ofs->copyup_wq);
-	spin_unlock(&ofs->copyup_wq.lock);
+	mutex_unlock(&OVL_I(d_inode(dentry))->lock);
 }
 
 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)