From c91192d66d6cea7878b8542c9d9f1873971aba92 Mon Sep 17 00:00:00 2001 From: Pavel Machek <pavel@suse.cz> Date: Thu, 15 Jan 2009 13:51:03 -0800 Subject: [PATCH] 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> --- drivers/block/nbd.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 7bcc1d8bc967..34f80fa6fed1 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -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); -- 2.30.9