1 files changed, 130 insertions, 0 deletions
diff --git a/fs/partitions/devfs.c b/fs/partitions/devfs.c
new file mode 100644
index 000000000000..87f50444fd39
--- /dev/null
+++ b/fs/partitions/devfs.c
@@ -0,0 +1,130 @@
+/*
+ * 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);
+}
+
+