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);
+}
+
+