[PATCH] beginning of probe_disk() and gendisks for floppy

That's a tricky one and large part of that stuff is temporary - it will be
replaced as soon as we have gendisks for all block devices and get sane
refcounting for gendisks.
	* we add per-major lists of gendisks; get_gendisk() looks into
appropriate list instead of looking through the list of all gendisks.
	* we allow driver to override that search - it can call
blk_set_probe(major, probe) and then gendisk will call probe(minor).
blk_set_probe(major, NULL) restores the default behaviour.
	* floppy.c switched to use of gendisks; we have one gendisk per
disk and let floppy_find(minor) return the right one.
	Note that final mechanism will involve a similar construction
but floppy.c is actually the least interesting application - places
where it will really play will include stuff like loading the right
high-level driver when we open /dev/hdX, etc.  And it won't be major-based...

drivers/block/floppy.c

@@ -416,6 +416,8 @@ static struct floppy_drive_params drive_params[N_DRIVE];
 static struct floppy_drive_struct drive_state[N_DRIVE];
 static struct floppy_write_errors write_errors[N_DRIVE];
 static struct timer_list motor_off_timer[N_DRIVE];
+static struct gendisk disks[N_DRIVE];
+static char names[N_DRIVE][4];
 static struct floppy_raw_cmd *raw_cmd, default_raw_cmd;
 
 /*
@@ -3775,6 +3777,7 @@ static int floppy_open(struct inode * inode, struct file * filp)
 	}
 
 	UDRS->fd_device = minor(inode->i_rdev);
+	set_capacity(&disks[drive], floppy_sizes[minor(inode->i_rdev)]);
 	if (old_dev != -1 && old_dev != minor(inode->i_rdev)) {
 		if (buffer_drive == drive)
 			buffer_track = -1;
@@ -3952,6 +3955,7 @@ static int floppy_revalidate(kdev_t dev)
 			poll_drive(0, FD_RAW_NEED_DISK);
 		process_fd_request();
 	}
+	set_capacity(&disks[drive], floppy_sizes[minor(dev)]);
 	return 0;
 }
 
@@ -4219,6 +4223,16 @@ static struct device device_floppy = {
 	bus_id:		"03?0",
 };
 
+static struct gendisk *floppy_find(int minor)
+{
+	int drive = (minor&3) | ((minor&0x80) >> 5);
+	if (drive >= N_DRIVE ||
+	    !(allowed_drive_mask & (1 << drive)) ||
+	    fdc_state[FDC(drive)].version == FDC_NONE)
+		return NULL;
+	return &disks[drive];
+}
+
 int __init floppy_init(void)
 {
 	int i,unit,drive;
@@ -4231,13 +4245,22 @@ int __init floppy_init(void)
 		return -EBUSY;
 	}
 
+	for (i=0; i<N_DRIVE; i++) {
+		disks[i].major = MAJOR_NR;
+		disks[i].first_minor = TOMINOR(i);
+		disks[i].fops = &floppy_fops;
+		sprintf(names[i], "fd%d", i);
+		disks[i].major_name = names[i];
+	}
+
+	blk_set_probe(MAJOR_NR, floppy_find);
+
 	for (i=0; i<256; i++)
 		if (ITYPE(i))
 			floppy_sizes[i] = (floppy_type[ITYPE(i)].size+1) >> 1;
 		else
 			floppy_sizes[i] = MAX_DISK_SIZE;
 
-	blk_size[MAJOR_NR] = floppy_sizes;
 	blk_init_queue(BLK_DEFAULT_QUEUE(MAJOR_NR), do_fd_request, &floppy_lock);
 	reschedule_timeout(MAXTIMEOUT, "floppy init", MAXTIMEOUT);
 	config_types();
@@ -4262,6 +4285,7 @@ int __init floppy_init(void)
 		unregister_blkdev(MAJOR_NR,"fd");
 		del_timer(&fd_timeout);
 		blk_cleanup_queue(BLK_DEFAULT_QUEUE(MAJOR_NR));
+		blk_set_probe(MAJOR_NR, NULL);
 		return -ENODEV;
 	}
 #if N_FDC > 1
@@ -4273,6 +4297,7 @@ int __init floppy_init(void)
 		del_timer(&fd_timeout);
 		blk_cleanup_queue(BLK_DEFAULT_QUEUE(MAJOR_NR));
 		unregister_blkdev(MAJOR_NR,"fd");
+		blk_set_probe(MAJOR_NR, NULL);
 		return -EBUSY;
 	}
 
@@ -4336,6 +4361,7 @@ int __init floppy_init(void)
 			floppy_release_irq_and_dma();
 		blk_cleanup_queue(BLK_DEFAULT_QUEUE(MAJOR_NR));
 		unregister_blkdev(MAJOR_NR,"fd");
+		blk_set_probe(MAJOR_NR, NULL);
 	}
 	
 	for (drive = 0; drive < N_DRIVE; drive++) {
@@ -4345,9 +4371,7 @@ int __init floppy_init(void)
 			continue;
 		if (fdc_state[FDC(drive)].version == FDC_NONE)
 			continue;
-		for (i = 0; i<NUMBER(floppy_type); i++)
-			register_disk(NULL, mk_kdev(MAJOR_NR,TOMINOR(drive)+i*4),
-					1, &floppy_fops, 0);
+		add_disk(disks + drive);
 	}
 
 	register_sys_device(&device_floppy);
@@ -4532,15 +4556,21 @@ int init_module(void)
 
 void cleanup_module(void)
 {
-	int dummy;
+	int i;
 		
 	unregister_sys_device(&device_floppy);
 	devfs_unregister (devfs_handle);
 	unregister_blkdev(MAJOR_NR, "fd");
+	blk_set_probe(MAJOR_NR, NULL);
+	for (drive = 0; drive < N_DRIVE; drive++) {
+		if ((allowed_drive_mask & (1 << drive)) &&
+		    fdc_state[FDC(drive)].version != FDC_NONE)
+			del_gendisk(disks + drive);
+	}
 
 	blk_cleanup_queue(BLK_DEFAULT_QUEUE(MAJOR_NR));
 	/* eject disk, if any */
-	dummy = fd_eject(0);
+	fd_eject(0);
 }
 
 MODULE_PARM(floppy,"s");

drivers/block/genhd.c

@@ -33,6 +33,23 @@ static rwlock_t gendisk_lock;
  */
 static struct gendisk *gendisk_head;
 
+/*
+ *  TEMPORARY KLUDGE.
+ */
+static struct {
+	struct list_head list;
+	struct gendisk *(*get)(int minor);
+} gendisks[MAX_BLKDEV];
+
+void blk_set_probe(int major, struct gendisk *(p)(int))
+{
+	write_lock(&gendisk_lock);
+	gendisks[major].get = p;
+	write_unlock(&gendisk_lock);
+}
+EXPORT_SYMBOL(blk_set_probe);	/* Will go away */
+	
+
 /**
  * add_gendisk - add partitioning information to kernel list
  * @gp: per-device partitioning information
@@ -42,7 +59,6 @@ static struct gendisk *gendisk_head;
  */
 static void add_gendisk(struct gendisk *gp)
 {
-	struct gendisk *sgp;
 	struct hd_struct *p = NULL;
 
 	if (gp->minor_shift) {
@@ -58,24 +74,9 @@ static void add_gendisk(struct gendisk *gp)
 	gp->part = p;
 
 	write_lock(&gendisk_lock);
-
-	/*
- 	 *	In 2.5 this will go away. Fix the drivers who rely on
- 	 *	old behaviour.
- 	 */
-
-	for (sgp = gendisk_head; sgp; sgp = sgp->next)
-	{
-		if (sgp == gp)
-		{
-			printk(KERN_ERR "add_gendisk: device major %d is buggy and added a live gendisk!\n",
-				sgp->major);
-			goto out;
-		}
-	}
+	list_add(&gp->list, &gendisks[gp->major].list);
 	gp->next = gendisk_head;
 	gendisk_head = gp;
-out:
 	write_unlock(&gendisk_lock);
 }
 
@@ -98,6 +99,7 @@ void unlink_gendisk(struct gendisk *disk)
 			break;
 	if (*p)
 		*p = (*p)->next;
+	list_del_init(&disk->list);
 	write_unlock(&gendisk_lock);
 }
 
@@ -111,20 +113,25 @@ void unlink_gendisk(struct gendisk *disk)
 struct gendisk *
 get_gendisk(kdev_t dev)
 {
-	struct gendisk *gp = NULL;
+	struct gendisk *disk;
+	struct list_head *p;
 	int major = major(dev);
 	int minor = minor(dev);
 
 	read_lock(&gendisk_lock);
-	for (gp = gendisk_head; gp; gp = gp->next) {
-		if (gp->major != major)
-			continue;
-		if (gp->first_minor > minor)
+	if (gendisks[major].get) {
+		disk = gendisks[major].get(minor);
+		read_unlock(&gendisk_lock);
+		return disk;
+	}
+	list_for_each(p, &gendisks[major].list) {
+		disk = list_entry(p, struct gendisk, list);
+		if (disk->first_minor > minor)
 			continue;
-		if (gp->first_minor + (1<<gp->minor_shift) <= minor)
+		if (disk->first_minor + (1<<disk->minor_shift) <= minor)
 			continue;
 		read_unlock(&gendisk_lock);
-		return gp;
+		return disk;
 	}
 	read_unlock(&gendisk_lock);
 	return NULL;
@@ -200,7 +207,10 @@ extern int cpqarray_init(void);
 
 int __init device_init(void)
 {
+	int i;
 	rwlock_init(&gendisk_lock);
+	for (i = 0; i < MAX_BLKDEV; i++)
+		INIT_LIST_HEAD(&gendisks[i].list);
 	blk_dev_init();
 #ifdef CONFIG_FC4_SOC
 	/* This has to be done before scsi_dev_init */

include/linux/genhd.h

@@ -81,6 +81,7 @@ struct gendisk {
 	struct gendisk *next;
 	struct block_device_operations *fops;
 	sector_t capacity;
+	struct list_head list;
 
 	int flags;
 	int number;			/* devfs crap */
@@ -260,6 +261,9 @@ char *disk_name (struct gendisk *hd, int part, char *buf);
 extern int rescan_partitions(struct gendisk *disk, struct block_device *bdev);
 extern void update_partition(struct gendisk *disk, int part);
 
+/* will go away */
+extern void blk_set_probe(int major, struct gendisk *(p)(int));
+
 static inline unsigned int disk_index (kdev_t dev)
 {
 	struct gendisk *g = get_gendisk(dev);