fs/partitions/devfs.c

   1 /*
   2  * This tries to keep block devices away from devfs as much as possible.
   3  */
   4 #include <linux/fs.h>
   5 #include <linux/devfs_fs_kernel.h>
   6 #include <linux/vmalloc.h>
   7 #include <linux/genhd.h>
   8 #include <linux/bitops.h>
   9 #include <asm/semaphore.h>
  10
  11
  12 struct unique_numspace {
  13         u32               num_free;          /*  Num free in bits       */
  14         u32               length;            /*  Array length in bytes  */
  15         unsigned long     *bits;
  16         struct semaphore  mutex;
  17 };
  18
  19 static DECLARE_MUTEX(numspace_mutex);
  20
  21 static int expand_numspace(struct unique_numspace *s)
  22 {
  23         u32 length;
  24         void *bits;
  25
  26         if (s->length < 16)
  27                 length = 16;
  28         else
  29                 length = s->length << 1;
  30
  31         bits = vmalloc(length);
  32         if (!bits)
  33                 return -ENOMEM;
  34         if (s->bits) {
  35                 memcpy(bits, s->bits, s->length);
  36                 vfree(s->bits);
  37         }
  38
  39         s->num_free = (length - s->length) << 3;
  40         s->bits = bits;
  41         memset(bits + s->length, 0, length - s->length);
  42         s->length = length;
  43
  44         return 0;
  45 }
  46
  47 static int alloc_unique_number(struct unique_numspace *s)
  48 {
  49         int rval = 0;
  50
  51         down(&numspace_mutex);
  52         if (s->num_free < 1)
  53                 rval = expand_numspace(s);
  54         if (!rval) {
  55                 rval = find_first_zero_bit(s->bits, s->length << 3);
  56                 --s->num_free;
  57                 __set_bit(rval, s->bits);
  58         }
  59         up(&numspace_mutex);
  60
  61         return rval;
  62 }
  63
  64 static void dealloc_unique_number(struct unique_numspace *s, int number)
  65 {
  66         int old_val;
  67
  68         if (number >= 0) {
  69                 down(&numspace_mutex);
  70                 old_val = __test_and_clear_bit(number, s->bits);
  71                 if (old_val)
  72                         ++s->num_free;
  73                 up(&numspace_mutex);
  74         }
  75 }
  76
  77 static struct unique_numspace disc_numspace;
  78 static struct unique_numspace cdrom_numspace;
  79
  80 void devfs_add_partitioned(struct gendisk *disk)
  81 {
  82         char dirname[64], symlink[16];
  83
  84         devfs_mk_dir(disk->devfs_name);
  85         devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),
  86                         S_IFBLK|S_IRUSR|S_IWUSR,
  87                         "%s/disc", disk->devfs_name);
  88
  89         disk->number = alloc_unique_number(&disc_numspace);
  90
  91         sprintf(symlink, "discs/disc%d", disk->number);
  92         sprintf(dirname, "../%s", disk->devfs_name);
  93         devfs_mk_symlink(symlink, dirname);
  94
  95 }
  96
  97 void devfs_add_disk(struct gendisk *disk)
  98 {
  99         devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),
 100                         (disk->flags & GENHD_FL_CD) ?
 101                                 S_IFBLK|S_IRUGO|S_IWUGO :
 102                                 S_IFBLK|S_IRUSR|S_IWUSR,
 103                         "%s", disk->devfs_name);
 104
 105         if (disk->flags & GENHD_FL_CD) {
 106                 char dirname[64], symlink[16];
 107
 108                 disk->number = alloc_unique_number(&cdrom_numspace);
 109
 110                 sprintf(symlink, "cdroms/cdrom%d", disk->number);
 111                 sprintf(dirname, "../%s", disk->devfs_name);
 112                 devfs_mk_symlink(symlink, dirname);
 113         }
 114 }
 115
 116 void devfs_remove_disk(struct gendisk *disk)
 117 {
 118         if (disk->minors != 1) {
 119                 devfs_remove("discs/disc%d", disk->number);
 120                 dealloc_unique_number(&disc_numspace, disk->number);
 121                 devfs_remove("%s/disc", disk->devfs_name);
 122         }
 123         if (disk->flags & GENHD_FL_CD) {
 124                 devfs_remove("cdroms/cdrom%d", disk->number);
 125                 dealloc_unique_number(&cdrom_numspace, disk->number);
 126         }
 127         devfs_remove(disk->devfs_name);
 128 }
 129
 130