[dm-devel] [PATCH 44/78] loop: use __register_blkdev to allocate devices on demand

[Christoph Hellwig]

Use the simpler mechanism attached to major_name to allocate a brd device
when a currently unregistered minor is accessed.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Hannes Reinecke <h...@suse.de>
---
 drivers/block/loop.c | 30 ++++++++----------------------
 1 file changed, 8 insertions(+), 22 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 41caf799df721f..9a27d4f1c08aac 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2231,24 +2231,18 @@ static int loop_lookup(struct loop_device **l, int i)
        return ret;
 }
 
-static struct kobject *loop_probe(dev_t dev, int *part, void *data)
+static void loop_probe(dev_t dev)
 {
+       int idx = MINOR(dev) >> part_shift;
        struct loop_device *lo;
-       struct kobject *kobj;
-       int err;
+
+       if (max_loop && idx >= max_loop)
+               return;
 
        mutex_lock(&loop_ctl_mutex);
-       err = loop_lookup(&lo, MINOR(dev) >> part_shift);
-       if (err < 0)
-               err = loop_add(&lo, MINOR(dev) >> part_shift);
-       if (err < 0)
-               kobj = NULL;
-       else
-               kobj = get_disk_and_module(lo->lo_disk);
+       if (loop_lookup(&lo, idx) < 0)
+               loop_add(&lo, idx);
        mutex_unlock(&loop_ctl_mutex);
-
-       *part = 0;
-       return kobj;
 }
 
 static long loop_control_ioctl(struct file *file, unsigned int cmd,
@@ -2368,14 +2362,11 @@ static int __init loop_init(void)
                goto err_out;
 
 
-       if (register_blkdev(LOOP_MAJOR, "loop")) {
+       if (__register_blkdev(LOOP_MAJOR, "loop", loop_probe)) {
                err = -EIO;
                goto misc_out;
        }
 
-       blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
-                                 THIS_MODULE, loop_probe, NULL, NULL);
-
        /* pre-create number of devices given by config or max_loop */
        mutex_lock(&loop_ctl_mutex);
        for (i = 0; i < nr; i++)
@@ -2401,16 +2392,11 @@ static int loop_exit_cb(int id, void *ptr, void *data)
 
 static void __exit loop_exit(void)
 {
-       unsigned long range;
-
-       range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
-
        mutex_lock(&loop_ctl_mutex);
 
        idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
        idr_destroy(&loop_index_idr);
 
-       blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
        unregister_blkdev(LOOP_MAJOR, "loop");
 
        misc_deregister(&loop_misc);
-- 
2.29.2

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