xref: /openbmc/linux/arch/s390/hypfs/hypfs_dbfs.c (revision b34e08d5)
1 /*
2  * Hypervisor filesystem for Linux on s390 - debugfs interface
3  *
4  * Copyright IBM Corp. 2010
5  * Author(s): Michael Holzheu <holzheu@linux.vnet.ibm.com>
6  */
7 
8 #include <linux/slab.h>
9 #include "hypfs.h"
10 
11 static struct dentry *dbfs_dir;
12 
13 static struct hypfs_dbfs_data *hypfs_dbfs_data_alloc(struct hypfs_dbfs_file *f)
14 {
15 	struct hypfs_dbfs_data *data;
16 
17 	data = kmalloc(sizeof(*data), GFP_KERNEL);
18 	if (!data)
19 		return NULL;
20 	kref_init(&data->kref);
21 	data->dbfs_file = f;
22 	return data;
23 }
24 
25 static void hypfs_dbfs_data_free(struct kref *kref)
26 {
27 	struct hypfs_dbfs_data *data;
28 
29 	data = container_of(kref, struct hypfs_dbfs_data, kref);
30 	data->dbfs_file->data_free(data->buf_free_ptr);
31 	kfree(data);
32 }
33 
34 static void data_free_delayed(struct work_struct *work)
35 {
36 	struct hypfs_dbfs_data *data;
37 	struct hypfs_dbfs_file *df;
38 
39 	df = container_of(work, struct hypfs_dbfs_file, data_free_work.work);
40 	mutex_lock(&df->lock);
41 	data = df->data;
42 	df->data = NULL;
43 	mutex_unlock(&df->lock);
44 	kref_put(&data->kref, hypfs_dbfs_data_free);
45 }
46 
47 static ssize_t dbfs_read(struct file *file, char __user *buf,
48 			 size_t size, loff_t *ppos)
49 {
50 	struct hypfs_dbfs_data *data;
51 	struct hypfs_dbfs_file *df;
52 	ssize_t rc;
53 
54 	if (*ppos != 0)
55 		return 0;
56 
57 	df = file_inode(file)->i_private;
58 	mutex_lock(&df->lock);
59 	if (!df->data) {
60 		data = hypfs_dbfs_data_alloc(df);
61 		if (!data) {
62 			mutex_unlock(&df->lock);
63 			return -ENOMEM;
64 		}
65 		rc = df->data_create(&data->buf, &data->buf_free_ptr,
66 				     &data->size);
67 		if (rc) {
68 			mutex_unlock(&df->lock);
69 			kfree(data);
70 			return rc;
71 		}
72 		df->data = data;
73 		schedule_delayed_work(&df->data_free_work, HZ);
74 	}
75 	data = df->data;
76 	kref_get(&data->kref);
77 	mutex_unlock(&df->lock);
78 
79 	rc = simple_read_from_buffer(buf, size, ppos, data->buf, data->size);
80 	kref_put(&data->kref, hypfs_dbfs_data_free);
81 	return rc;
82 }
83 
84 static long dbfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
85 {
86 	struct hypfs_dbfs_file *df;
87 	long rc;
88 
89 	df = file->f_path.dentry->d_inode->i_private;
90 	mutex_lock(&df->lock);
91 	if (df->unlocked_ioctl)
92 		rc = df->unlocked_ioctl(file, cmd, arg);
93 	else
94 		rc = -ENOTTY;
95 	mutex_unlock(&df->lock);
96 	return rc;
97 }
98 
99 static const struct file_operations dbfs_ops = {
100 	.read		= dbfs_read,
101 	.llseek		= no_llseek,
102 	.unlocked_ioctl = dbfs_ioctl,
103 };
104 
105 int hypfs_dbfs_create_file(struct hypfs_dbfs_file *df)
106 {
107 	df->dentry = debugfs_create_file(df->name, 0400, dbfs_dir, df,
108 					 &dbfs_ops);
109 	if (IS_ERR(df->dentry))
110 		return PTR_ERR(df->dentry);
111 	mutex_init(&df->lock);
112 	INIT_DELAYED_WORK(&df->data_free_work, data_free_delayed);
113 	return 0;
114 }
115 
116 void hypfs_dbfs_remove_file(struct hypfs_dbfs_file *df)
117 {
118 	debugfs_remove(df->dentry);
119 }
120 
121 int hypfs_dbfs_init(void)
122 {
123 	dbfs_dir = debugfs_create_dir("s390_hypfs", NULL);
124 	return PTR_ERR_OR_ZERO(dbfs_dir);
125 }
126 
127 void hypfs_dbfs_exit(void)
128 {
129 	debugfs_remove(dbfs_dir);
130 }
131