Re: [PATCH 06/26] brd: convert to blk_alloc_disk/blk_cleanup_disk

Hannes Reinecke
2021-05-23T07:58:54Z

On 5/21/21 7:50 AM, Christoph Hellwig wrote:
> Convert the brd driver to use the blk_alloc_disk and blk_cleanup_disk
> helpers to simplify gendisk and request_queue allocation. This also
> allows to remove the request_queue pointer in struct request_queue,
> and to simplify the initialization as blk_cleanup_disk can be called
> on any disk returned from blk_alloc_disk.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/block/brd.c | 94 ++++++++++++++++-----------------------------
> 1 file changed, 33 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
> index 7562cf30b14e..95694113e38e 100644
> --- a/drivers/block/brd.c
> +++ b/drivers/block/brd.c
> @@ -38,9 +38,7 @@
> * device).
> */
> struct brd_device {
> - int brd_number;
> -
> - struct request_queue *brd_queue;
> + int brd_number;
> struct gendisk *brd_disk;
> struct list_head brd_list;
>
> @@ -372,7 +370,7 @@ static LIST_HEAD(brd_devices);
> static DEFINE_MUTEX(brd_devices_mutex);
> static struct dentry *brd_debugfs_dir;
>
> -static struct brd_device *brd_alloc(int i)
> +static int brd_alloc(int i)
> {
> struct brd_device *brd;
> struct gendisk *disk;
> @@ -380,64 +378,55 @@ static struct brd_device *brd_alloc(int i)
>
> brd = kzalloc(sizeof(*brd), GFP_KERNEL);
> if (!brd)
> - goto out;
> + return -ENOMEM;
> brd->brd_number = i;
> spin_lock_init(&brd->brd_lock);
> INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
>
> - brd->brd_queue = blk_alloc_queue(NUMA_NO_NODE);
> - if (!brd->brd_queue)
> - goto out_free_dev;
> -
> snprintf(buf, DISK_NAME_LEN, "ram%d", i);
> if (!IS_ERR_OR_NULL(brd_debugfs_dir))
> debugfs_create_u64(buf, 0444, brd_debugfs_dir,
> &brd->brd_nr_pages);
>
> - /* This is so fdisk will align partitions on 4k, because of
> - * direct_access API needing 4k alignment, returning a PFN
> - * (This is only a problem on very small devices <= 4M,
> - * otherwise fdisk will align on 1M. Regardless this call
> - * is harmless)
> - */
> - blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
> - disk = brd->brd_disk = alloc_disk(max_part);
> + disk = brd->brd_disk = blk_alloc_disk(NUMA_NO_NODE);
> if (!disk)
> - goto out_free_queue;
> + goto out_free_dev;
> +
> disk->major = RAMDISK_MAJOR;
> disk->first_minor = i * max_part;
> + disk->minors = max_part;
> disk->fops = &brd_fops;
> disk->private_data = brd;
> disk->flags = GENHD_FL_EXT_DEVT;
> strlcpy(disk->disk_name, buf, DISK_NAME_LEN);
> set_capacity(disk, rd_size * 2);
> +
> + /*
> + * This is so fdisk will align partitions on 4k, because of
> + * direct_access API needing 4k alignment, returning a PFN
> + * (This is only a problem on very small devices <= 4M,
> + * otherwise fdisk will align on 1M. Regardless this call
> + * is harmless)
> + */
> + blk_queue_physical_block_size(disk->queue, PAGE_SIZE);
>

Maybe converting the comment to refer to 'PAGE_SIZE' instead of 4k while
you're at it ...

> /* Tell the block layer that this is not a rotational device */
> - blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue);
> - blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, brd->brd_queue);
> + blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
> + blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
> + add_disk(disk);
> + list_add_tail(&brd->brd_list, &brd_devices);
>
> - return brd;
> + return 0;
>
> -out_free_queue:
> - blk_cleanup_queue(brd->brd_queue);
> out_free_dev:
> kfree(brd);
> -out:
> - return NULL;
> -}
> -
> -static void brd_free(struct brd_device *brd)
> -{
> - put_disk(brd->brd_disk);
> - blk_cleanup_queue(brd->brd_queue);
> - brd_free_pages(brd);
> - kfree(brd);
> + return -ENOMEM;
> }
>
> static void brd_probe(dev_t dev)
> {
> - struct brd_device *brd;
> int i = MINOR(dev) / max_part;
> + struct brd_device *brd;
>
> mutex_lock(&brd_devices_mutex);
> list_for_each_entry(brd, &brd_devices, brd_list) {
> @@ -445,13 +434,7 @@ static void brd_probe(dev_t dev)
> goto out_unlock;
> }
>
> - brd = brd_alloc(i);
> - if (brd) {
> - brd->brd_disk->queue = brd->brd_queue;
> - add_disk(brd->brd_disk);
> - list_add_tail(&brd->brd_list, &brd_devices);
> - }
> -
> + brd_alloc(i);
> out_unlock:
> mutex_unlock(&brd_devices_mutex);
> }
> @@ -460,7 +443,9 @@ static void brd_del_one(struct brd_device *brd)
> {
> list_del(&brd->brd_list);
> del_gendisk(brd->brd_disk);
> - brd_free(brd);
> + blk_cleanup_disk(brd->brd_disk);
> + brd_free_pages(brd);
> + kfree(brd);
> }
>
> static inline void brd_check_and_reset_par(void)
> @@ -485,7 +470,7 @@ static inline void brd_check_and_reset_par(void)
> static int __init brd_init(void)
> {
> struct brd_device *brd, *next;
> - int i;
> + int err, i;
>
> /*
> * brd module now has a feature to instantiate underlying device
> @@ -511,22 +496,11 @@ static int __init brd_init(void)
>
> mutex_lock(&brd_devices_mutex);
> for (i = 0; i < rd_nr; i++) {
> - brd = brd_alloc(i);
> - if (!brd)
> + err = brd_alloc(i);
> + if (err)
> goto out_free;
> - list_add_tail(&brd->brd_list, &brd_devices);
> }
>
> - /* point of no return */
> -
> - list_for_each_entry(brd, &brd_devices, brd_list) {
> - /*
> - * associate with queue just before adding disk for
> - * avoiding to mess up failure path
> - */
> - brd->brd_disk->queue = brd->brd_queue;
> - add_disk(brd->brd_disk);
> - }
> mutex_unlock(&brd_devices_mutex);
>
> pr_info("brd: module loaded\n");
> @@ -535,15 +509,13 @@ static int __init brd_init(void)
> out_free:
> debugfs_remove_recursive(brd_debugfs_dir);
>
> - list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
> - list_del(&brd->brd_list);
> - brd_free(brd);
> - }
> + list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
> + brd_del_one(brd);
> mutex_unlock(&brd_devices_mutex);
> unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
>
> pr_info("brd: module NOT loaded !!!\n");
> - return -ENOMEM;
> + return err;
> }
>
> static void __exit brd_exit(void)
>
Other than that:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
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