linux-kernel - [PATCH 1/5] block: add disk sequence number

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Message-Id: <20210206000903.215028-2-mcroce@linux.microsoft.com>
Date:   Sat,  6 Feb 2021 01:08:59 +0100
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Lennart Poettering <lennart@...ttering.net>,
        Luca Boccassi <bluca@...ian.org>, Jens Axboe <axboe@...nel.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 1/5] block: add disk sequence number

From: Matteo Croce <mcroce@...rosoft.com>

Add a sequence number to the disk devices. This number is put in the
uevent so userspace can correlate events when a driver reuses a device,
like the loop one.

Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
---
 block/genhd.c         | 19 +++++++++++++++++++
 include/linux/genhd.h |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index 9e741a4f351b..4dbf589e1610 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1425,8 +1425,17 @@ static void disk_release(struct device *dev)
 		blk_put_queue(disk->queue);
 	kfree(disk);
 }
+
+static int block_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+
+	return add_uevent_var(env, "DISKSEQ=%llu", disk->diskseq);
+}
+
 struct class block_class = {
 	.name		= "block",
+	.dev_uevent	= block_uevent,
 };
 
 static char *block_devnode(struct device *dev, umode_t *mode,
@@ -1601,6 +1610,8 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
 	disk_to_dev(disk)->class = &block_class;
 	disk_to_dev(disk)->type = &disk_type;
 	device_initialize(disk_to_dev(disk));
+	inc_diskseq(disk);
+
 	return disk;
 
 out_bdput:
@@ -2149,3 +2160,11 @@ static void disk_release_events(struct gendisk *disk)
 	WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
 	kfree(disk->ev);
 }
+
+void inc_diskseq(struct gendisk *disk)
+{
+	static atomic64_t diskseq;
+
+	disk->diskseq = atomic64_inc_return(&diskseq);
+}
+EXPORT_SYMBOL_GPL(inc_diskseq);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 809aaa32d53c..2e5a0b8893db 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -177,6 +177,7 @@ struct gendisk {
 	int node_id;
 	struct badblocks *bb;
 	struct lockdep_map lockdep_map;
+	u64 diskseq;
 };
 
 /*
@@ -335,6 +336,7 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
 #endif /* CONFIG_SYSFS */
 
 extern struct rw_semaphore bdev_lookup_sem;
+extern void inc_diskseq(struct gendisk *disk);
 
 dev_t blk_lookup_devt(const char *name, int partno);
 void blk_request_module(dev_t devt);
-- 
2.29.2