linux-kernel - [PATCH 3.2 135/185] dm bufio: initialize read-only module parameters

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Date:	Sun, 29 Dec 2013 03:08:44 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Mikulas Patocka" <mpatocka@...hat.com>,
	"Mike Snitzer" <snitzer@...hat.com>
Subject: [PATCH 3.2 135/185] dm bufio: initialize read-only module parameters

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mikulas Patocka <mpatocka@...hat.com>

commit 4cb57ab4a2e61978f3a9b7d4f53988f30d61c27f upstream.

Some module parameters in dm-bufio are read-only. These parameters
inform the user about memory consumption. They are not supposed to be
changed by the user.

However, despite being read-only, these parameters can be set on
modprobe or insmod command line, for example:
modprobe dm-bufio current_allocated_bytes=12345

The kernel doesn't expect that these variables can be non-zero at module
initialization and if the user sets them, it results in BUG.

This patch initializes the variables in the module init routine, so that
user-supplied values are ignored.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/dm-bufio.c | 5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1611,6 +1611,11 @@ static int __init dm_bufio_init(void)
 {
 	__u64 mem;
 
+	dm_bufio_allocated_kmem_cache = 0;
+	dm_bufio_allocated_get_free_pages = 0;
+	dm_bufio_allocated_vmalloc = 0;
+	dm_bufio_current_allocated = 0;
+
 	memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
 	memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
 

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