nullb: add configfs interface

Add configfs interface for nullb. configfs interface is more flexible
and easy to configure in a per-disk basis.

Configuration is something like this:
mount -t configfs none /mnt

Checking which features the driver supports:
cat /mnt/nullb/features

The 'features' attribute is for future extension. We probably will add
new features into the driver, userspace can check this attribute to find
the supported features.

Create/remove a device:
mkdir/rmdir /mnt/nullb/a

Then configure the device by setting attributes under /mnt/nullb/a, most
of nullb supported module parameters are converted to attributes:
size; /* device size in MB */
completion_nsec; /* time in ns to complete a request */
submit_queues; /* number of submission queues */
home_node; /* home node for the device */
queue_mode; /* block interface */
blocksize; /* block size */
irqmode; /* IRQ completion handler */
hw_queue_depth; /* queue depth */
use_lightnvm; /* register as a LightNVM device */
blocking; /* blocking blk-mq device */
use_per_node_hctx; /* use per-node allocation for hardware context */

Note, creating a device doesn't create a disk immediately. Creating a
disk is done in two phases: create a device and then power on the
device. Next patch will introduce device power on.

Based on original patch from Kyungchan Koh

Signed-off-by: Kyungchan Koh <kkc6196@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 8ddc982..5dd62a8 100644 (file)
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -17,6 +17,7 @@ if BLK_DEV
 
 config BLK_DEV_NULL_BLK
        tristate "Null test block driver"
+       depends on CONFIGFS_FS
 
 config BLK_DEV_FD
        tristate "Normal floppy disk support"

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 73938cd..c782492 100644 (file)
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -1,3 +1,7 @@
+/*
+ * Add configfs and memory store: Kyungchan Koh <kkc6196@fb.com> and
+ * Shaohua Li <shli@fb.com>
+ */
 #include <linux/module.h>
 
 #include <linux/moduleparam.h>
@@ -9,6 +13,7 @@
 #include <linux/blk-mq.h>
 #include <linux/hrtimer.h>
 #include <linux/lightnvm.h>
+#include <linux/configfs.h>
 
 struct nullb_cmd {
        struct list_head list;
@@ -30,8 +35,21 @@ struct nullb_queue {
        struct nullb_cmd *cmds;
 };
 
+/*
+ * Status flags for nullb_device.
+ *
+ * CONFIGURED: Device has been configured and turned on. Cannot reconfigure.
+ * UP:         Device is currently on and visible in userspace.
+ */
+enum nullb_device_flags {
+       NULLB_DEV_FL_CONFIGURED = 0,
+       NULLB_DEV_FL_UP         = 1,
+};
+
 struct nullb_device {
        struct nullb *nullb;
+       struct config_item item;
+       unsigned long flags; /* device flags */
 
        unsigned long size; /* device size in MB */
        unsigned long completion_nsec; /* time in ns to complete a request */
@@ -173,6 +191,185 @@ static bool g_use_per_node_hctx;
 module_param_named(use_per_node_hctx, g_use_per_node_hctx, bool, S_IRUGO);
 MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");
 
+static struct nullb_device *null_alloc_dev(void);
+static void null_free_dev(struct nullb_device *dev);
+
+static inline struct nullb_device *to_nullb_device(struct config_item *item)
+{
+       return item ? container_of(item, struct nullb_device, item) : NULL;
+}
+
+static inline ssize_t nullb_device_uint_attr_show(unsigned int val, char *page)
+{
+       return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static inline ssize_t nullb_device_ulong_attr_show(unsigned long val,
+       char *page)
+{
+       return snprintf(page, PAGE_SIZE, "%lu\n", val);
+}
+
+static inline ssize_t nullb_device_bool_attr_show(bool val, char *page)
+{
+       return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t nullb_device_uint_attr_store(unsigned int *val,
+       const char *page, size_t count)
+{
+       unsigned int tmp;
+       int result;
+
+       result = kstrtouint(page, 0, &tmp);
+       if (result)
+               return result;
+
+       *val = tmp;
+       return count;
+}
+
+static ssize_t nullb_device_ulong_attr_store(unsigned long *val,
+       const char *page, size_t count)
+{
+       int result;
+       unsigned long tmp;
+
+       result = kstrtoul(page, 0, &tmp);
+       if (result)
+               return result;
+
+       *val = tmp;
+       return count;
+}
+
+static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
+       size_t count)
+{
+       bool tmp;
+       int result;
+
+       result = kstrtobool(page,  &tmp);
+       if (result)
+               return result;
+
+       *val = tmp;
+       return count;
+}
+
+/* The following macro should only be used with TYPE = {uint, ulong, bool}. */
+#define NULLB_DEVICE_ATTR(NAME, TYPE)                                          \
+static ssize_t                                                                 \
+nullb_device_##NAME##_show(struct config_item *item, char *page)               \
+{                                                                              \
+       return nullb_device_##TYPE##_attr_show(                                 \
+                               to_nullb_device(item)->NAME, page);             \
+}                                                                              \
+static ssize_t                                                                 \
+nullb_device_##NAME##_store(struct config_item *item, const char *page,                \
+                           size_t count)                                       \
+{                                                                              \
+       if (test_bit(NULLB_DEV_FL_CONFIGURED, &to_nullb_device(item)->flags))   \
+               return -EBUSY;                                                  \
+       return nullb_device_##TYPE##_attr_store(                                \
+                       &to_nullb_device(item)->NAME, page, count);             \
+}                                                                              \
+CONFIGFS_ATTR(nullb_device_, NAME);
+
+NULLB_DEVICE_ATTR(size, ulong);
+NULLB_DEVICE_ATTR(completion_nsec, ulong);
+NULLB_DEVICE_ATTR(submit_queues, uint);
+NULLB_DEVICE_ATTR(home_node, uint);
+NULLB_DEVICE_ATTR(queue_mode, uint);
+NULLB_DEVICE_ATTR(blocksize, uint);
+NULLB_DEVICE_ATTR(irqmode, uint);
+NULLB_DEVICE_ATTR(hw_queue_depth, uint);
+NULLB_DEVICE_ATTR(use_lightnvm, bool);
+NULLB_DEVICE_ATTR(blocking, bool);
+NULLB_DEVICE_ATTR(use_per_node_hctx, bool);
+
+static struct configfs_attribute *nullb_device_attrs[] = {
+       &nullb_device_attr_size,
+       &nullb_device_attr_completion_nsec,
+       &nullb_device_attr_submit_queues,
+       &nullb_device_attr_home_node,
+       &nullb_device_attr_queue_mode,
+       &nullb_device_attr_blocksize,
+       &nullb_device_attr_irqmode,
+       &nullb_device_attr_hw_queue_depth,
+       &nullb_device_attr_use_lightnvm,
+       &nullb_device_attr_blocking,
+       &nullb_device_attr_use_per_node_hctx,
+       NULL,
+};
+
+static void nullb_device_release(struct config_item *item)
+{
+       null_free_dev(to_nullb_device(item));
+}
+
+static struct configfs_item_operations nullb_device_ops = {
+       .release        = nullb_device_release,
+};
+
+static struct config_item_type nullb_device_type = {
+       .ct_item_ops    = &nullb_device_ops,
+       .ct_attrs       = nullb_device_attrs,
+       .ct_owner       = THIS_MODULE,
+};
+
+static struct
+config_item *nullb_group_make_item(struct config_group *group, const char *name)
+{
+       struct nullb_device *dev;
+
+       dev = null_alloc_dev();
+       if (!dev)
+               return ERR_PTR(-ENOMEM);
+
+       config_item_init_type_name(&dev->item, name, &nullb_device_type);
+
+       return &dev->item;
+}
+
+static void
+nullb_group_drop_item(struct config_group *group, struct config_item *item)
+{
+       config_item_put(item);
+}
+
+static ssize_t memb_group_features_show(struct config_item *item, char *page)
+{
+       return snprintf(page, PAGE_SIZE, "\n");
+}
+
+CONFIGFS_ATTR_RO(memb_group_, features);
+
+static struct configfs_attribute *nullb_group_attrs[] = {
+       &memb_group_attr_features,
+       NULL,
+};
+
+static struct configfs_group_operations nullb_group_ops = {
+       .make_item      = nullb_group_make_item,
+       .drop_item      = nullb_group_drop_item,
+};
+
+static struct config_item_type nullb_group_type = {
+       .ct_group_ops   = &nullb_group_ops,
+       .ct_attrs       = nullb_group_attrs,
+       .ct_owner       = THIS_MODULE,
+};
+
+static struct configfs_subsystem nullb_subsys = {
+       .su_group = {
+               .cg_item = {
+                       .ci_namebuf = "nullb",
+                       .ci_type = &nullb_group_type,
+               },
+       },
+};
+
 static struct nullb_device *null_alloc_dev(void)
 {
        struct nullb_device *dev;
@@ -919,12 +1116,19 @@ static int __init null_init(void)
                        return ret;
        }
 
+       config_group_init(&nullb_subsys.su_group);
+       mutex_init(&nullb_subsys.su_mutex);
+
+       ret = configfs_register_subsystem(&nullb_subsys);
+       if (ret)
+               goto err_tagset;
+
        mutex_init(&lock);
 
        null_major = register_blkdev(0, "nullb");
        if (null_major < 0) {
                ret = null_major;
-               goto err_tagset;
+               goto err_conf;
        }
 
        if (g_use_lightnvm) {
@@ -961,6 +1165,8 @@ err_dev:
        kmem_cache_destroy(ppa_cache);
 err_ppa:
        unregister_blkdev(null_major, "nullb");
+err_conf:
+       configfs_unregister_subsystem(&nullb_subsys);
 err_tagset:
        if (g_queue_mode == NULL_Q_MQ && shared_tags)
                blk_mq_free_tag_set(&tag_set);
@@ -971,6 +1177,8 @@ static void __exit null_exit(void)
 {
        struct nullb *nullb;
 
+       configfs_unregister_subsystem(&nullb_subsys);
+
        unregister_blkdev(null_major, "nullb");
 
        mutex_lock(&lock);