[PATCH v12 12/12] bcache: add sysfs interface register_nvdimm_meta to register NVDIMM meta device

[Coly Li <colyli@suse.de>]

This patch adds a sysfs interface register_nvdimm_meta to register
NVDIMM meta device. The sysfs interface file only shows up when
CONFIG_BCACHE_NVM_PAGES=y. Then a NVDIMM name space formatted by
bcache-tools can be registered into bcache by e.g.,
  echo /dev/pmem0 > /sys/fs/bcache/register_nvdimm_meta

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jianpeng Ma <jianpeng.ma@intel.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
---
 drivers/md/bcache/super.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 24734250d005..434739594baf 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2403,10 +2403,18 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 static ssize_t bch_pending_bdevs_cleanup(struct kobject *k,
 					 struct kobj_attribute *attr,
 					 const char *buffer, size_t size);
+#if defined(CONFIG_BCACHE_NVM_PAGES)
+static ssize_t register_nvdimm_meta(struct kobject *k,
+				    struct kobj_attribute *attr,
+				    const char *buffer, size_t size);
+#endif
 
 kobj_attribute_write(register,		register_bcache);
 kobj_attribute_write(register_quiet,	register_bcache);
 kobj_attribute_write(pendings_cleanup,	bch_pending_bdevs_cleanup);
+#if defined(CONFIG_BCACHE_NVM_PAGES)
+kobj_attribute_write(register_nvdimm_meta, register_nvdimm_meta);
+#endif
 
 static bool bch_is_open_backing(dev_t dev)
 {
@@ -2520,6 +2528,24 @@ static void register_device_async(struct async_reg_args *args)
 	queue_delayed_work(system_wq, &args->reg_work, 10);
 }
 
+#if defined(CONFIG_BCACHE_NVM_PAGES)
+static ssize_t register_nvdimm_meta(struct kobject *k, struct kobj_attribute *attr,
+				    const char *buffer, size_t size)
+{
+	ssize_t ret = size;
+
+	struct bch_nvmpg_ns *ns = bch_register_namespace(buffer);
+
+	if (IS_ERR(ns)) {
+		pr_err("register nvdimm namespace %s for meta device failed.\n",
+			buffer);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+#endif
+
 static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 			       const char *buffer, size_t size)
 {
@@ -2855,6 +2881,9 @@ static int __init bcache_init(void)
 	static const struct attribute *files[] = {
 		&ksysfs_register.attr,
 		&ksysfs_register_quiet.attr,
+#if defined(CONFIG_BCACHE_NVM_PAGES)
+		&ksysfs_register_nvdimm_meta.attr,
+#endif
 		&ksysfs_pendings_cleanup.attr,
 		NULL
 	};
-- 
2.26.2