Re: dm: change dm_get_target_type() to check for module load error

From: Shuah Khan
Date: Wed Oct 06 2021 - 16:55:42 EST


On 10/6/21 2:35 PM, Mike Snitzer wrote:
On Mon, Oct 04 2021 at 4:06P -0400,
Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:

dm_get_target_type() doesn't check error return from request_module().
Change to check for error and return NULL instead of trying to get
target type again which would fail.

Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-target.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 64dd0b34fcf4..0789e9f91d3a 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -41,17 +41,22 @@ static struct target_type *get_target_type(const char *name)
return tt;
}
-static void load_module(const char *name)
+static int load_module(const char *name)
{
- request_module("dm-%s", name);
+ return request_module("dm-%s", name);
}
struct target_type *dm_get_target_type(const char *name)
{
struct target_type *tt = get_target_type(name);
+ int ret;
if (!tt) {
- load_module(name);
+ ret = load_module(name);
+ if (ret < 0) {
+ pr_err("Module %s load failed %d\n", name, ret);
+ return NULL;
+ }
tt = get_target_type(name);
}
--
2.30.2


While I appreciate your intent, the reality is that multiple targets
may be made available in a given module. And so loading one dm module
may bring in access to N targets. There isn't a rigid 1:1 mapping of
target modules to names. And there may not even be a loadable module
that has the name dm-${name} -- but that doesn't mean the target_type
won;t have been loaded into DM for it to access.


Thanks for the explanation.

-- Shuah