diff mbox series

[v3,3/4] block: add support for notifications

Message ID 609f654800583feb016d96d9c3fc2f029f0f460a.1719368448.git.daniel@makrotopia.org (mailing list archive)
State New
Headers show
Series block: preparations for NVMEM provider | expand

Commit Message

Daniel Golle June 26, 2024, 2:51 a.m. UTC 
Add notifier block to notify other subsystems about the addition or
removal of block devices.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 block/Kconfig          |  6 +++
 block/Makefile         |  1 +
 block/blk-notify.c     | 88 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h |  8 ++++
 4 files changed, 103 insertions(+)
 create mode 100644 block/blk-notify.c

Comments

Jens Axboe June 26, 2024, 7:46 p.m. UTC | #1 
On 6/25/24 8:51 PM, Daniel Golle wrote:
> +static int blk_call_notifier_add(struct device *dev)
> +{
> +	struct blk_device_list *new_blkdev;
> +
> +	new_blkdev = kmalloc(sizeof(*new_blkdev), GFP_KERNEL);
> +	if (!new_blkdev)
> +		return -ENOMEM;
> +
> +	new_blkdev->dev = dev;
> +	mutex_lock(&blk_notifier_lock);
> +	list_add_tail(&new_blkdev->list, &blk_devices);
> +	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_ADD, dev);
> +	mutex_unlock(&blk_notifier_lock);
> +
> +	return 0;
> +}

Nit: redundant newline.

> +device_initcall(blk_notifications_init);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index b2f1362c4681..8d22ba03e3e1 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1687,4 +1687,12 @@ static inline bool bdev_can_atomic_write(struct block_device *bdev)
>  
>  #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
>  
> +
> +#ifdef CONFIG_BLOCK_NOTIFIERS

#if defined(CONFIG_BLOCK_NOTIFIERS)

> +#define BLK_DEVICE_ADD		1
> +#define BLK_DEVICE_REMOVE	2
> +void blk_register_notify(struct notifier_block *nb);
> +void blk_unregister_notify(struct notifier_block *nb);
> +#endif

Surely these helpers should have a !CONFIG_BLOCK_NOTIFIERS failure case
definition? Either that, or dummies. As it stands, any caller would need
to check if it's enabled or not.
Daniel Golle June 26, 2024, 7:55 p.m. UTC | #2 
Hi Jens,

thanks a lot for the review!

On Wed, Jun 26, 2024 at 01:46:50PM -0600, Jens Axboe wrote:
> On 6/25/24 8:51 PM, Daniel Golle wrote:
> > +static int blk_call_notifier_add(struct device *dev)
> > +{
> > +	struct blk_device_list *new_blkdev;
> > +
> > +	new_blkdev = kmalloc(sizeof(*new_blkdev), GFP_KERNEL);
> > +	if (!new_blkdev)
> > +		return -ENOMEM;
> > +
> > +	new_blkdev->dev = dev;
> > +	mutex_lock(&blk_notifier_lock);
> > +	list_add_tail(&new_blkdev->list, &blk_devices);
> > +	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_ADD, dev);
> > +	mutex_unlock(&blk_notifier_lock);
> > +
> > +	return 0;
> > +}
> 
> Nit: redundant newline.

I'll remove the newline before the 'return' statement then, right?

> 
> > +device_initcall(blk_notifications_init);
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index b2f1362c4681..8d22ba03e3e1 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -1687,4 +1687,12 @@ static inline bool bdev_can_atomic_write(struct block_device *bdev)
> >  
> >  #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
> >  
> > +
> > +#ifdef CONFIG_BLOCK_NOTIFIERS
> 
> #if defined(CONFIG_BLOCK_NOTIFIERS)
> 
> > +#define BLK_DEVICE_ADD		1
> > +#define BLK_DEVICE_REMOVE	2
> > +void blk_register_notify(struct notifier_block *nb);
> > +void blk_unregister_notify(struct notifier_block *nb);
> > +#endif
> 
> Surely these helpers should have a !CONFIG_BLOCK_NOTIFIERS failure case
> definition? Either that, or dummies. As it stands, any caller would need
> to check if it's enabled or not.

Makes sense. I'll add dummies to the header and always define
the macros for notification types.

Note that what I'm planning to do is to have the block nvmem provider
select CONFIG_BLOCK_NOTIFIERS in Kconfig, as without that it simply
won't work at all.


Cheers


Daniel
Jens Axboe June 26, 2024, 8:23 p.m. UTC | #3 
On 6/26/24 1:55 PM, Daniel Golle wrote:
> Hi Jens,
> 
> thanks a lot for the review!
> 
> On Wed, Jun 26, 2024 at 01:46:50PM -0600, Jens Axboe wrote:
>> On 6/25/24 8:51 PM, Daniel Golle wrote:
>>> +static int blk_call_notifier_add(struct device *dev)
>>> +{
>>> +	struct blk_device_list *new_blkdev;
>>> +
>>> +	new_blkdev = kmalloc(sizeof(*new_blkdev), GFP_KERNEL);
>>> +	if (!new_blkdev)
>>> +		return -ENOMEM;
>>> +
>>> +	new_blkdev->dev = dev;
>>> +	mutex_lock(&blk_notifier_lock);
>>> +	list_add_tail(&new_blkdev->list, &blk_devices);
>>> +	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_ADD, dev);
>>> +	mutex_unlock(&blk_notifier_lock);
>>> +
>>> +	return 0;
>>> +}
>>
>> Nit: redundant newline.
> 
> I'll remove the newline before the 'return' statement then, right?

Yup

>>> +device_initcall(blk_notifications_init);
>>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>>> index b2f1362c4681..8d22ba03e3e1 100644
>>> --- a/include/linux/blkdev.h
>>> +++ b/include/linux/blkdev.h
>>> @@ -1687,4 +1687,12 @@ static inline bool bdev_can_atomic_write(struct block_device *bdev)
>>>  
>>>  #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
>>>  
>>> +
>>> +#ifdef CONFIG_BLOCK_NOTIFIERS
>>
>> #if defined(CONFIG_BLOCK_NOTIFIERS)
>>
>>> +#define BLK_DEVICE_ADD		1
>>> +#define BLK_DEVICE_REMOVE	2
>>> +void blk_register_notify(struct notifier_block *nb);
>>> +void blk_unregister_notify(struct notifier_block *nb);
>>> +#endif
>>
>> Surely these helpers should have a !CONFIG_BLOCK_NOTIFIERS failure case
>> definition? Either that, or dummies. As it stands, any caller would need
>> to check if it's enabled or not.
> 
> Makes sense. I'll add dummies to the header and always define
> the macros for notification types.

Exactly

> Note that what I'm planning to do is to have the block nvmem provider
> select CONFIG_BLOCK_NOTIFIERS in Kconfig, as without that it simply
> won't work at all.

Right, but then someone else uses them for something else, and then
we'll need it anyway.
diff mbox series

Patch

diff --git a/block/Kconfig b/block/Kconfig
index 5b623b876d3b..67cd4f92378a 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -209,6 +209,12 @@  config BLK_INLINE_ENCRYPTION_FALLBACK
 	  by falling back to the kernel crypto API when inline
 	  encryption hardware is not present.
 
+config BLOCK_NOTIFIERS
+	bool "Enable support for notifications in block layer"
+	help
+	  Enable this option to provide notifiers for other subsystems
+	  upon addition or removal of block devices.
+
 source "block/partitions/Kconfig"
 
 config BLK_MQ_PCI
diff --git a/block/Makefile b/block/Makefile
index ddfd21c1a9ff..a131fa7d6b26 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -38,3 +38,4 @@  obj-$(CONFIG_BLK_INLINE_ENCRYPTION)	+= blk-crypto.o blk-crypto-profile.o \
 					   blk-crypto-sysfs.o
 obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)	+= blk-crypto-fallback.o
 obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)	+= holder.o
+obj-$(CONFIG_BLOCK_NOTIFIERS) += blk-notify.o
diff --git a/block/blk-notify.c b/block/blk-notify.c
new file mode 100644
index 000000000000..594df7aa7be0
--- /dev/null
+++ b/block/blk-notify.c
@@ -0,0 +1,88 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Notifiers for addition and removal of block devices
+ *
+ * Copyright (c) 2024 Daniel Golle <daniel@makrotopia.org>
+ */
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+
+#include "blk.h"
+
+struct blk_device_list {
+	struct device *dev;
+	struct list_head list;
+};
+
+static RAW_NOTIFIER_HEAD(blk_notifier_list);
+static DEFINE_MUTEX(blk_notifier_lock);
+static LIST_HEAD(blk_devices);
+
+void blk_register_notify(struct notifier_block *nb)
+{
+	struct blk_device_list *existing_blkdev;
+
+	mutex_lock(&blk_notifier_lock);
+	raw_notifier_chain_register(&blk_notifier_list, nb);
+
+	list_for_each_entry(existing_blkdev, &blk_devices, list)
+		nb->notifier_call(nb, BLK_DEVICE_ADD, existing_blkdev->dev);
+
+	mutex_unlock(&blk_notifier_lock);
+}
+EXPORT_SYMBOL_GPL(blk_register_notify);
+
+void blk_unregister_notify(struct notifier_block *nb)
+{
+	mutex_lock(&blk_notifier_lock);
+	raw_notifier_chain_unregister(&blk_notifier_list, nb);
+	mutex_unlock(&blk_notifier_lock);
+}
+EXPORT_SYMBOL_GPL(blk_unregister_notify);
+
+static int blk_call_notifier_add(struct device *dev)
+{
+	struct blk_device_list *new_blkdev;
+
+	new_blkdev = kmalloc(sizeof(*new_blkdev), GFP_KERNEL);
+	if (!new_blkdev)
+		return -ENOMEM;
+
+	new_blkdev->dev = dev;
+	mutex_lock(&blk_notifier_lock);
+	list_add_tail(&new_blkdev->list, &blk_devices);
+	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_ADD, dev);
+	mutex_unlock(&blk_notifier_lock);
+
+	return 0;
+}
+
+static void blk_call_notifier_remove(struct device *dev)
+{
+	struct blk_device_list *old_blkdev, *tmp;
+
+	mutex_lock(&blk_notifier_lock);
+	list_for_each_entry_safe(old_blkdev, tmp, &blk_devices, list) {
+		if (old_blkdev->dev != dev)
+			continue;
+
+		list_del(&old_blkdev->list);
+		kfree(old_blkdev);
+	}
+	raw_notifier_call_chain(&blk_notifier_list, BLK_DEVICE_REMOVE, dev);
+	mutex_unlock(&blk_notifier_lock);
+}
+
+static struct class_interface blk_notifications_bus_interface __refdata = {
+	.class = &block_class,
+	.add_dev = &blk_call_notifier_add,
+	.remove_dev = &blk_call_notifier_remove,
+};
+
+static int __init blk_notifications_init(void)
+{
+	return class_interface_register(&blk_notifications_bus_interface);
+}
+device_initcall(blk_notifications_init);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b2f1362c4681..8d22ba03e3e1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1687,4 +1687,12 @@  static inline bool bdev_can_atomic_write(struct block_device *bdev)
 
 #define DEFINE_IO_COMP_BATCH(name)	struct io_comp_batch name = { }
 
+
+#ifdef CONFIG_BLOCK_NOTIFIERS
+#define BLK_DEVICE_ADD		1
+#define BLK_DEVICE_REMOVE	2
+void blk_register_notify(struct notifier_block *nb);
+void blk_unregister_notify(struct notifier_block *nb);
+#endif
+
 #endif /* _LINUX_BLKDEV_H */