hfsplus: switch to ->iterate_shared()

We need to protect the list of hfsplus_readdir_data against parallel
insertions (in readdir) and removals (in release).  Add a spinlock
for that.  Note that it has nothing to do with protection of
hfsplus_readdir_data->key - we have an exclusion between hfsplus_readdir()
and hfsplus_delete_cat() on directory lock and between several
hfsplus_readdir() for the same struct file on ->f_pos_lock.  The spinlock
is strictly for list changes.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/hfsplus/catalog.c

@@ -374,12 +374,15 @@ int hfsplus_delete_cat(u32 cnid, struct inode *dir, struct qstr *str)
 		hfsplus_free_fork(sb, cnid, &fork, HFSPLUS_TYPE_RSRC);
 	}
 
+	/* we only need to take spinlock for exclusion with ->release() */
+	spin_lock(&HFSPLUS_I(dir)->open_dir_lock);
 	list_for_each(pos, &HFSPLUS_I(dir)->open_dir_list) {
 		struct hfsplus_readdir_data *rd =
 			list_entry(pos, struct hfsplus_readdir_data, list);
 		if (fd.tree->keycmp(fd.search_key, (void *)&rd->key) < 0)
 			rd->file->f_pos--;
 	}
+	spin_unlock(&HFSPLUS_I(dir)->open_dir_lock);
 
 	err = hfs_brec_remove(&fd);
 	if (err)

fs/hfsplus/dir.c

@@ -271,8 +271,14 @@ static int hfsplus_readdir(struct file *file, struct dir_context *ctx)
 		}
 		file->private_data = rd;
 		rd->file = file;
+		spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
 		list_add(&rd->list, &HFSPLUS_I(inode)->open_dir_list);
+		spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
 	}
+	/*
+	 * Can be done after the list insertion; exclusion with
+	 * hfsplus_delete_cat() is provided by directory lock.
+	 */
 	memcpy(&rd->key, fd.key, sizeof(struct hfsplus_cat_key));
 out:
 	kfree(strbuf);
@@ -284,9 +290,9 @@ static int hfsplus_dir_release(struct inode *inode, struct file *file)
 {
 	struct hfsplus_readdir_data *rd = file->private_data;
 	if (rd) {
-		inode_lock(inode);
+		spin_lock(&HFSPLUS_I(inode)->open_dir_lock);
 		list_del(&rd->list);
-		inode_unlock(inode);
+		spin_unlock(&HFSPLUS_I(inode)->open_dir_lock);
 		kfree(rd);
 	}
 	return 0;
@@ -569,7 +575,7 @@ const struct inode_operations hfsplus_dir_inode_operations = {
 const struct file_operations hfsplus_dir_operations = {
 	.fsync		= hfsplus_file_fsync,
 	.read		= generic_read_dir,
-	.iterate	= hfsplus_readdir,
+	.iterate_shared	= hfsplus_readdir,
 	.unlocked_ioctl = hfsplus_ioctl,
 	.llseek		= generic_file_llseek,
 	.release	= hfsplus_dir_release,

fs/hfsplus/hfsplus_fs.h

@@ -244,6 +244,7 @@ struct hfsplus_inode_info {
 	u8 userflags;		/* BSD user file flags */
 	u32 subfolders;		/* Subfolder count (HFSX only) */
 	struct list_head open_dir_list;
+	spinlock_t open_dir_lock;
 	loff_t phys_size;
 
 	struct inode vfs_inode;

fs/hfsplus/inode.c

@@ -374,6 +374,7 @@ struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode)
 
 	hip = HFSPLUS_I(inode);
 	INIT_LIST_HEAD(&hip->open_dir_list);
+	spin_lock_init(&hip->open_dir_lock);
 	mutex_init(&hip->extents_lock);
 	atomic_set(&hip->opencnt, 0);
 	hip->extent_state = 0;

fs/hfsplus/super.c

@@ -67,6 +67,7 @@ struct inode *hfsplus_iget(struct super_block *sb, unsigned long ino)
 		return inode;
 
 	INIT_LIST_HEAD(&HFSPLUS_I(inode)->open_dir_list);
+	spin_lock_init(&HFSPLUS_I(inode)->open_dir_lock);
 	mutex_init(&HFSPLUS_I(inode)->extents_lock);
 	HFSPLUS_I(inode)->flags = 0;
 	HFSPLUS_I(inode)->extent_state = 0;