Commit c91192d6 authored Jan 15, 2009 by Pavel Machek Committed by Linus Torvalds Jan 15, 2009

nbd: do not allow two clients at the same time



Two nbd-clients at same time are bad idea, and cause WARN_ON from nbd in
2.6.28-rc7 from sysfs_add_one.  This simply prevents that from happening.

To reproduce:

 cat /dev/zero | head -c 10000000 > /tmp/delme.fstest.fs
 nbd-server 9100 -l /anyone.can.connect > /tmp/delme.fstest.fs &
 sleep 1
 nbd-client localhost 9100 /dev/nd0 &
 nbd-client localhost 9100 /dev/nd0 &

Signed-off-by: Pavel Machek <pavel@suse.cz>
Acked-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1bcbf313

drivers/block/nbd.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -406,6 +406,7 @@ static int nbd_do_it(struct nbd_device *lo)
		ret = sysfs_create_file(&disk_to_dev(lo->disk)->kobj, &pid_attr.attr);
		if (ret) {
		printk(KERN_ERR "nbd: sysfs_create_file failed!");
		lo->pid = 0;
		return ret;
		}

		@@ -413,6 +414,7 @@ static int nbd_do_it(struct nbd_device *lo)
		nbd_end_request(req);

		sysfs_remove_file(&disk_to_dev(lo->disk)->kobj, &pid_attr.attr);
		lo->pid = 0;
		return 0;
		}

		@@ -648,6 +650,8 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
		set_capacity(lo->disk, lo->bytesize >> 9);
		return 0;
		case NBD_DO_IT:
		if (lo->pid)
		return -EBUSY;
		if (!lo->file)
		return -EINVAL;
		thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);