[PATCH 51/78] z2ram: use separate gendisk for the different modes

[Christoph Hellwig <hch@xxxxxx>]

Use separate gendisks (which share a tag_set) for the different operating
modes instead of redirecting the gendisk lookup using a probe callback.
This avoids potential problems with aliased block_device instances and
will eventually allow for removing the blk_register_region framework.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
---
 drivers/block/z2ram.c | 100 ++++++++++++++++++++++++------------------
 1 file changed, 58 insertions(+), 42 deletions(-)

diff --git a/drivers/block/z2ram.c b/drivers/block/z2ram.c
index eafecc9a72b38d..c1d20818e64920 100644
--- a/drivers/block/z2ram.c
+++ b/drivers/block/z2ram.c
@@ -63,7 +63,7 @@ static int current_device = -1;
 
 static DEFINE_SPINLOCK(z2ram_lock);
 
-static struct gendisk *z2ram_gendisk;
+static struct gendisk *z2ram_gendisk[Z2MINOR_COUNT];
 
 static blk_status_t z2_queue_rq(struct blk_mq_hw_ctx *hctx,
                                const struct blk_mq_queue_data *bd)
@@ -283,7 +283,7 @@ static int z2_open(struct block_device *bdev, fmode_t mode)
 
                current_device = device;
                z2ram_size <<= Z2RAM_CHUNKSHIFT;
-               set_capacity(z2ram_gendisk, z2ram_size >> 9);
+               set_capacity(z2ram_gendisk[device], z2ram_size >> 9);
        }
 
        mutex_unlock(&z2ram_mutex);
@@ -315,71 +315,87 @@ static const struct block_device_operations z2_fops = {
        .release = z2_release,
 };
 
-static struct kobject *z2_find(dev_t dev, int *part, void *data)
-{
-       *part = 0;
-       return get_disk_and_module(z2ram_gendisk);
-}
-
-static struct request_queue *z2_queue;
 static struct blk_mq_tag_set tag_set;
 
 static const struct blk_mq_ops z2_mq_ops = {
        .queue_rq = z2_queue_rq,
 };
 
+static int z2ram_register_disk(int minor)
+{
+       struct request_queue *q;
+       struct gendisk *disk;
+
+       disk = alloc_disk(1);
+       if (!disk)
+               return -ENOMEM;
+
+       q = blk_mq_init_queue(&tag_set);
+       if (IS_ERR(q)) {
+               put_disk(disk);
+               return PTR_ERR(q);
+       }
+
+       disk->major = Z2RAM_MAJOR;
+       disk->first_minor = minor;
+       disk->fops = &z2_fops;
+       if (minor)
+               sprintf(disk->disk_name, "z2ram%d", minor);
+       else
+               sprintf(disk->disk_name, "z2ram");
+       disk->queue = q;
+
+       z2ram_gendisk[minor] = disk;
+       add_disk(disk);
+       return 0;
+}
+
 static int __init z2_init(void)
 {
-       int ret;
+       int ret, i;
 
        if (!MACH_IS_AMIGA)
                return -ENODEV;
 
-       ret = -EBUSY;
        if (register_blkdev(Z2RAM_MAJOR, DEVICE_NAME))
-               goto err;
-
-       ret = -ENOMEM;
-       z2ram_gendisk = alloc_disk(1);
-       if (!z2ram_gendisk)
-               goto out_disk;
-
-       z2_queue = blk_mq_init_sq_queue(&tag_set, &z2_mq_ops, 16,
-                                       BLK_MQ_F_SHOULD_MERGE);
-       if (IS_ERR(z2_queue)) {
-               ret = PTR_ERR(z2_queue);
-               z2_queue = NULL;
-               goto out_queue;
+               return -EBUSY;
+
+       tag_set.ops = &z2_mq_ops;
+       tag_set.nr_hw_queues = 1;
+       tag_set.nr_maps = 1;
+       tag_set.queue_depth = 16;
+       tag_set.numa_node = NUMA_NO_NODE;
+       tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+       ret = blk_mq_alloc_tag_set(&tag_set);
+       if (ret)
+               goto out_unregister_blkdev;
+
+       for (i = 0; i < Z2MINOR_COUNT; i++) {
+               ret = z2ram_register_disk(i);
+               if (ret && i == 0)
+                       goto out_free_tagset;
        }
 
-       z2ram_gendisk->major = Z2RAM_MAJOR;
-       z2ram_gendisk->first_minor = 0;
-       z2ram_gendisk->fops = &z2_fops;
-       sprintf(z2ram_gendisk->disk_name, "z2ram");
-
-       z2ram_gendisk->queue = z2_queue;
-       add_disk(z2ram_gendisk);
-       blk_register_region(MKDEV(Z2RAM_MAJOR, 0), Z2MINOR_COUNT, THIS_MODULE,
-                           z2_find, NULL, NULL);
-
        return 0;
 
-out_queue:
-       put_disk(z2ram_gendisk);
-out_disk:
+out_free_tagset:
+       blk_mq_free_tag_set(&tag_set);
+out_unregister_blkdev:
        unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
-err:
        return ret;
 }
 
 static void __exit z2_exit(void)
 {
        int i, j;
-       blk_unregister_region(MKDEV(Z2RAM_MAJOR, 0), Z2MINOR_COUNT);
+
        unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
-       del_gendisk(z2ram_gendisk);
-       put_disk(z2ram_gendisk);
-       blk_cleanup_queue(z2_queue);
+
+       for (i = 0; i < Z2MINOR_COUNT; i++) {
+               del_gendisk(z2ram_gendisk[i]);
+               blk_cleanup_queue(z2ram_gendisk[i]->queue);
+               put_disk(z2ram_gendisk[i]);
+       }
        blk_mq_free_tag_set(&tag_set);
 
        if (current_device != -1) {
-- 
2.29.2