linux-kernel - [PATCH v2 03/12] virtio-blk: Generate uevent after attribute available

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Message-Id: <20160630015953.6888-4-famz@redhat.com>
Date:	Thu, 30 Jun 2016 09:59:44 +0800
From:	Fam Zheng <famz@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Jens Axboe <axboe@...nel.dk>,
	"Ed L. Cashin" <ed.cashin@....org>, Jiri Kosina <jikos@...nel.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Minchan Kim <minchan@...nel.org>,
	Nitin Gupta <ngupta@...are.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Shaohua Li <shli@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Keith Busch <keith.busch@...el.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-block@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-raid@...r.kernel.org, linux-mmc@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-nvme@...ts.infradead.org,
	Christoph Hellwig <hch@...radead.org>, famz@...hat.com
Subject: [PATCH v2 03/12] virtio-blk: Generate uevent after attribute available

Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that
point we haven't created the serial attribute file, therefore depending
on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get
created.

This race condition can be easily reproduced by hot plugging a number of
virtio-blk disks.

Also in systemd, there used to be a related workaround in udev rules
called 'WAIT_FOR="serial"', but it is removed in later versions.

Now let's generate a KOBJ_CHANGE event after the attributes are ready.

Signed-off-by: Fam Zheng <famz@...hat.com>
---
 drivers/block/virtio_blk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index f3a59f9..cd9a036 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -733,7 +733,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 
 	virtio_device_ready(vdev);
 
-	add_disk(vblk->disk, true);
+	add_disk(vblk->disk, false);
 	err = device_create_file(disk_to_dev(vblk->disk), &dev_attr_serial);
 	if (err)
 		goto out_del_disk;
@@ -746,6 +746,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 					 &dev_attr_cache_type_ro);
 	if (err)
 		goto out_del_disk;
+	disk_gen_uevents(vblk->disk);
 	return 0;
 
 out_del_disk:
-- 
2.9.0