drivers/xen/xenfs/super.c

   1 /*
   2  *  xenfs.c - a filesystem for passing info between the a domain and
   3  *  the hypervisor.
   4  *
   5  * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
   6  *                              and /proc/xen compatibility mount point.
   7  *                              Turned xenfs into a loadable module.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/magic.h>
  15 #include <linux/mm.h>
  16 #include <linux/backing-dev.h>
  17
  18 #include <xen/xen.h>
  19
  20 #include "xenfs.h"
  21
  22 #include <asm/xen/hypervisor.h>
  23
  24 MODULE_DESCRIPTION("Xen filesystem");
  25 MODULE_LICENSE("GPL");
  26
  27 static int xenfs_set_page_dirty(struct page *page)
  28 {
  29         if (!PageDirty(page))
  30                 SetPageDirty(page);
  31         return 0;
  32 }
  33
  34 static const struct address_space_operations xenfs_aops = {
  35         .set_page_dirty = xenfs_set_page_dirty,
  36 };
  37
  38 static struct backing_dev_info xenfs_backing_dev_info = {
  39         .ra_pages       = 0,    /* No readahead */
  40         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  41 };
  42
  43 static struct inode *xenfs_make_inode(struct super_block *sb, int mode)
  44 {
  45         struct inode *ret = new_inode(sb);
  46
  47         if (ret) {
  48                 ret->i_mode = mode;
  49                 ret->i_mapping->a_ops = &xenfs_aops;
  50                 ret->i_mapping->backing_dev_info = &xenfs_backing_dev_info;
  51                 ret->i_uid = ret->i_gid = 0;
  52                 ret->i_blocks = 0;
  53                 ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
  54         }
  55         return ret;
  56 }
  57
  58 static struct dentry *xenfs_create_file(struct super_block *sb,
  59                                         struct dentry *parent,
  60                                         const char *name,
  61                                         const struct file_operations *fops,
  62                                         void *data,
  63                                         int mode)
  64 {
  65         struct dentry *dentry;
  66         struct inode *inode;
  67
  68         dentry = d_alloc_name(parent, name);
  69         if (!dentry)
  70                 return NULL;
  71
  72         inode = xenfs_make_inode(sb, S_IFREG | mode);
  73         if (!inode) {
  74                 dput(dentry);
  75                 return NULL;
  76         }
  77
  78         inode->i_fop = fops;
  79         inode->i_private = data;
  80
  81         d_add(dentry, inode);
  82         return dentry;
  83 }
  84
  85 static ssize_t capabilities_read(struct file *file, char __user *buf,
  86                                  size_t size, loff_t *off)
  87 {
  88         char *tmp = "";
  89
  90         if (xen_initial_domain())
  91                 tmp = "control_d\n";
  92
  93         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  94 }
  95
  96 static const struct file_operations capabilities_file_ops = {
  97         .read = capabilities_read,
  98 };
  99
 100 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
 101 {
 102         static struct tree_descr xenfs_files[] = {
 103                 [1] = {},
 104                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
 105                 { "capabilities", &capabilities_file_ops, S_IRUGO },
 106                 {""},
 107         };
 108         int rc;
 109
 110         rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
 111         if (rc < 0)
 112                 return rc;
 113
 114         if (xen_initial_domain()) {
 115                 xenfs_create_file(sb, sb->s_root, "xsd_kva",
 116                                   &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
 117                 xenfs_create_file(sb, sb->s_root, "xsd_port",
 118                                   &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
 119                 xenfs_create_file(sb, sb->s_root, "privcmd",
 120                                   &privcmd_file_ops, NULL, S_IRUSR|S_IWUSR);
 121         }
 122
 123         return rc;
 124 }
 125
 126 static int xenfs_get_sb(struct file_system_type *fs_type,
 127                         int flags, const char *dev_name,
 128                         void *data, struct vfsmount *mnt)
 129 {
 130         return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
 131 }
 132
 133 static struct file_system_type xenfs_type = {
 134         .owner =        THIS_MODULE,
 135         .name =         "xenfs",
 136         .get_sb =       xenfs_get_sb,
 137         .kill_sb =      kill_litter_super,
 138 };
 139
 140 static int __init xenfs_init(void)
 141 {
 142         int err;
 143         if (!xen_domain()) {
 144                 printk(KERN_INFO "xenfs: not registering filesystem on non-xen platform\n");
 145                 return 0;
 146         }
 147
 148         err = register_filesystem(&xenfs_type);
 149         if (err) {
 150                 printk(KERN_ERR "xenfs: Unable to register filesystem!\n");
 151                 goto out;
 152         }
 153
 154         err = bdi_init(&xenfs_backing_dev_info);
 155         if (err)
 156                 unregister_filesystem(&xenfs_type);
 157
 158  out:
 159
 160         return err;
 161 }
 162
 163 static void __exit xenfs_exit(void)
 164 {
 165         if (xen_domain())
 166                 unregister_filesystem(&xenfs_type);
 167 }
 168
 169 module_init(xenfs_init);
 170 module_exit(xenfs_exit);
 171