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

Daniel Golle
2024-06-26T02:51:29Z

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

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 */
--
2.45.2