lightnvm: allow targets to use sysfs

In order to register through the sysfs interface, a driver needs to know
its kobject. On a disk structure, this happens when the partition
information is added (device_add_disk), which for lightnvm takes place
after the target has been initialized. This means that on target
initialization, the kboject has not been created yet.

This patch adds a target function to let targets initialize their own
kboject as a child of the disk kobject.
Signed-off-by: Javier González <javier@cnexlabs.com>
Added exit typedef and passed gendisk instead of void pointer for exit.
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/core.c

@@ -289,6 +289,9 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create)
 	set_capacity(tdisk, tt->capacity(targetdata));
 	add_disk(tdisk);
 
+	if (tt->sysfs_init && tt->sysfs_init(tdisk))
+		goto err_sysfs;
+
 	t->type = tt;
 	t->disk = tdisk;
 	t->dev = tgt_dev;
@@ -298,6 +301,9 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create)
 	mutex_unlock(&dev->mlock);
 
 	return 0;
+err_sysfs:
+	if (tt->exit)
+		tt->exit(targetdata);
 err_init:
 	put_disk(tdisk);
 err_queue:
@@ -320,6 +326,9 @@ static void __nvm_remove_target(struct nvm_target *t)
 	del_gendisk(tdisk);
 	blk_cleanup_queue(q);
 
+	if (tt->sysfs_exit)
+		tt->sysfs_exit(tdisk);
+
 	if (tt->exit)
 		tt->exit(tdisk->private_data);
 

include/linux/lightnvm.h

@@ -440,6 +440,8 @@ typedef blk_qc_t (nvm_tgt_make_rq_fn)(struct request_queue *, struct bio *);
 typedef sector_t (nvm_tgt_capacity_fn)(void *);
 typedef void *(nvm_tgt_init_fn)(struct nvm_tgt_dev *, struct gendisk *);
 typedef void (nvm_tgt_exit_fn)(void *);
+typedef int (nvm_tgt_sysfs_init_fn)(struct gendisk *);
+typedef void (nvm_tgt_sysfs_exit_fn)(struct gendisk *);
 
 struct nvm_tgt_type {
 	const char *name;
@@ -453,6 +455,10 @@ struct nvm_tgt_type {
 	nvm_tgt_init_fn *init;
 	nvm_tgt_exit_fn *exit;
 
+	/* sysfs */
+	nvm_tgt_sysfs_init_fn *sysfs_init;
+	nvm_tgt_sysfs_exit_fn *sysfs_exit;
+
 	/* For internal use */
 	struct list_head list;
 };