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Message-Id: <20191104212143.389494354@linuxfoundation.org>
Date: Mon, 4 Nov 2019 22:44:51 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Mike Christie <mchristi@...hat.com>,
Josef Bacik <josef@...icpanda.com>,
Xiubo Li <xiubli@...hat.com>, Jens Axboe <axboe@...nel.dk>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 098/149] nbd: fix possible sysfs duplicate warning
From: Xiubo Li <xiubli@...hat.com>
[ Upstream commit 862488105b84ca744b3d8ff131e0fcfe10644be1 ]
1. nbd_put takes the mutex and drops nbd->ref to 0. It then does
idr_remove and drops the mutex.
2. nbd_genl_connect takes the mutex. idr_find/idr_for_each fails
to find an existing device, so it does nbd_dev_add.
3. just before the nbd_put could call nbd_dev_remove or not finished
totally, but if nbd_dev_add try to add_disk, we can hit:
debugfs: Directory 'nbd1' with parent 'block' already present!
This patch will make sure all the disk add/remove stuff are done
by holding the nbd_index_mutex lock.
Reported-by: Mike Christie <mchristi@...hat.com>
Reviewed-by: Josef Bacik <josef@...icpanda.com>
Signed-off-by: Xiubo Li <xiubli@...hat.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/block/nbd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index bc2fa4e85f0ca..d445195945618 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -228,8 +228,8 @@ static void nbd_put(struct nbd_device *nbd)
if (refcount_dec_and_mutex_lock(&nbd->refs,
&nbd_index_mutex)) {
idr_remove(&nbd_index_idr, nbd->index);
- mutex_unlock(&nbd_index_mutex);
nbd_dev_remove(nbd);
+ mutex_unlock(&nbd_index_mutex);
}
}
--
2.20.1
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