arch/s390/hypfs/hypfs_dbfs.c

   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         data->dbfs_file = f;
  21         return data;
  22 }
  23
  24 static void hypfs_dbfs_data_free(struct hypfs_dbfs_data *data)
  25 {
  26         data->dbfs_file->data_free(data->buf_free_ptr);
  27         kfree(data);
  28 }
  29
  30 static ssize_t dbfs_read(struct file *file, char __user *buf,
  31                          size_t size, loff_t *ppos)
  32 {
  33         struct hypfs_dbfs_data *data;
  34         struct hypfs_dbfs_file *df;
  35         ssize_t rc;
  36
  37         if (*ppos != 0)
  38                 return 0;
  39
  40         df = file_inode(file)->i_private;
  41         mutex_lock(&df->lock);
  42         data = hypfs_dbfs_data_alloc(df);
  43         if (!data) {
  44                 mutex_unlock(&df->lock);
  45                 return -ENOMEM;
  46         }
  47         rc = df->data_create(&data->buf, &data->buf_free_ptr, &data->size);
  48         if (rc) {
  49                 mutex_unlock(&df->lock);
  50                 kfree(data);
  51                 return rc;
  52         }
  53         mutex_unlock(&df->lock);
  54
  55         rc = simple_read_from_buffer(buf, size, ppos, data->buf, data->size);
  56         hypfs_dbfs_data_free(data);
  57         return rc;
  58 }
  59
  60 static long dbfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  61 {
  62         struct hypfs_dbfs_file *df = file_inode(file)->i_private;
  63         long rc;
  64
  65         mutex_lock(&df->lock);
  66         if (df->unlocked_ioctl)
  67                 rc = df->unlocked_ioctl(file, cmd, arg);
  68         else
  69                 rc = -ENOTTY;
  70         mutex_unlock(&df->lock);
  71         return rc;
  72 }
  73
  74 static const struct file_operations dbfs_ops = {
  75         .read           = dbfs_read,
  76         .llseek         = no_llseek,
  77         .unlocked_ioctl = dbfs_ioctl,
  78 };
  79
  80 int hypfs_dbfs_create_file(struct hypfs_dbfs_file *df)
  81 {
  82         df->dentry = debugfs_create_file(df->name, 0400, dbfs_dir, df,
  83                                          &dbfs_ops);
  84         if (IS_ERR(df->dentry))
  85                 return PTR_ERR(df->dentry);
  86         mutex_init(&df->lock);
  87         return 0;
  88 }
  89
  90 void hypfs_dbfs_remove_file(struct hypfs_dbfs_file *df)
  91 {
  92         debugfs_remove(df->dentry);
  93 }
  94
  95 int hypfs_dbfs_init(void)
  96 {
  97         dbfs_dir = debugfs_create_dir("s390_hypfs", NULL);
  98         return PTR_ERR_OR_ZERO(dbfs_dir);
  99 }
 100
 101 void hypfs_dbfs_exit(void)
 102 {
 103         debugfs_remove(dbfs_dir);
 104 }