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

Ben Hutchings
2013-12-29T02:08:44Z

From: Mikulas Patocka <mpatocka@redhat.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@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.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);