[dm-devel] [PATCH 1/2] dm-bufio: initialize read-only module parameters

[Mikulas Patocka]

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

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Cc: stable at kernel.org	# 3.2+

---
 drivers/md/dm-bufio.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-3.13-rc2/drivers/md/dm-bufio.c
===================================================================
--- linux-3.13-rc2.orig/drivers/md/dm-bufio.c	2013-12-05 23:23:02.000000000 +0100
+++ linux-3.13-rc2/drivers/md/dm-bufio.c	2013-12-05 23:26:37.000000000 +0100
@@ -1717,6 +1717,11 @@ 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);