bdi: register sysfs bdi device only once per queue

[Kay Sievers <kay.sievers@vrfy.org>]

Andrew, can you pick this up this please?

Thanks,
Kay


From: Kay Sievers <kay.sievers@vrfy.org>
Subject: bdi: register sysfs bdi device only once per queue

Devices which share the same queue, like floppies and mtd devices,
get registered multiple times in the bdi interface, but bdi accounts
only the last registered device of the devices sharing one queue.

On remove, all earlier registered devices leak, stay around in
sysfs, and cause "duplicate filename" errors if the devices are
re-created.

This prevents the creation of multiple bdi interfaces per queue,
and the bdi device will carry the dev_t name of the block device
which is the first one registered, of the pool of devices using
the same queue.

Tested-By: Peter Korsgaard <jacmet@sunsite.dk>
Acked-By: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-Off-By: Kay Sievers <kay.sievers@vrfy.org>
---

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index f2e574d..e6676e5 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -176,6 +176,9 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 	int ret = 0;
 	struct device *dev;
 
+	if (bdi->dev)
+		goto exit;
+
 	va_start(args, fmt);
 	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
 	va_end(args);