aboutsummaryrefslogtreecommitdiffstats
path: root/fs/partitions/devfs.c
blob: 87f50444fd3932bcfe93550e51ac3f8ba265d52a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
/*
 * This tries to keep block devices away from devfs as much as possible.
 */
#include <linux/fs.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/bitops.h>
#include <asm/semaphore.h>


struct unique_numspace {
	u32		  num_free;          /*  Num free in bits       */
	u32		  length;            /*  Array length in bytes  */
	unsigned long	  *bits;
	struct semaphore  mutex;
};

static DECLARE_MUTEX(numspace_mutex);

static int expand_numspace(struct unique_numspace *s)
{
	u32 length;
	void *bits;

	if (s->length < 16)
		length = 16;
	else
		length = s->length << 1;

	bits = vmalloc(length);
	if (!bits)
		return -ENOMEM;
	if (s->bits) {
		memcpy(bits, s->bits, s->length);
		vfree(s->bits);
	}
		
	s->num_free = (length - s->length) << 3;
	s->bits = bits;
	memset(bits + s->length, 0, length - s->length);
	s->length = length;

	return 0;
}

static int alloc_unique_number(struct unique_numspace *s)
{
	int rval = 0;

	down(&numspace_mutex);
	if (s->num_free < 1)
		rval = expand_numspace(s);
	if (!rval) {
		rval = find_first_zero_bit(s->bits, s->length << 3);
		--s->num_free;
		__set_bit(rval, s->bits);
	}
	up(&numspace_mutex);

	return rval;
}

static void dealloc_unique_number(struct unique_numspace *s, int number)
{
	int old_val;

	if (number >= 0) {
		down(&numspace_mutex);
		old_val = __test_and_clear_bit(number, s->bits);
		if (old_val)
			++s->num_free;
		up(&numspace_mutex);
	}
}

static struct unique_numspace disc_numspace;
static struct unique_numspace cdrom_numspace;

void devfs_add_partitioned(struct gendisk *disk)
{
	char dirname[64], symlink[16];

	devfs_mk_dir(disk->devfs_name);
	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),
			S_IFBLK|S_IRUSR|S_IWUSR,
			"%s/disc", disk->devfs_name);

	disk->number = alloc_unique_number(&disc_numspace);

	sprintf(symlink, "discs/disc%d", disk->number);
	sprintf(dirname, "../%s", disk->devfs_name);
	devfs_mk_symlink(symlink, dirname);

}

void devfs_add_disk(struct gendisk *disk)
{
	devfs_mk_bdev(MKDEV(disk->major, disk->first_minor),
			(disk->flags & GENHD_FL_CD) ?
				S_IFBLK|S_IRUGO|S_IWUGO :
				S_IFBLK|S_IRUSR|S_IWUSR,
			"%s", disk->devfs_name);

	if (disk->flags & GENHD_FL_CD) {
		char dirname[64], symlink[16];

		disk->number = alloc_unique_number(&cdrom_numspace);

		sprintf(symlink, "cdroms/cdrom%d", disk->number);
		sprintf(dirname, "../%s", disk->devfs_name);
		devfs_mk_symlink(symlink, dirname);
	}
}

void devfs_remove_disk(struct gendisk *disk)
{
	if (disk->minors != 1) {
		devfs_remove("discs/disc%d", disk->number);
		dealloc_unique_number(&disc_numspace, disk->number);
		devfs_remove("%s/disc", disk->devfs_name);
	}
	if (disk->flags & GENHD_FL_CD) {
		devfs_remove("cdroms/cdrom%d", disk->number);
		dealloc_unique_number(&cdrom_numspace, disk->number);
	}
	devfs_remove(disk->devfs_name);
}