LU-16888 gss: fix ptlrpc_gss automatic loading

ptlrpc_gss kernel module is automatically loaded when a GSS security
flavor is enforced. Loading success is recorded in a static variable
in the ptlrpc module, which prevents further reloading in case
ptlrpc_gss is unloaded while keeping ptlrpc loaded.
Get rid of this static variable as it is not required in order to
avoid calling request_module("ptlrpc_gss") when not needed. Indeed,
once loaded, the static array policies[] has an entry at the
SPTLRPC_POLICY_GSS index, indicating that the ptlrpc_gss module is
loaded.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I9bb100a202fe9c3fc455a2ffba6ee6398e19b9bf
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51264
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/ptlrpc/sec.c b/lustre/ptlrpc/sec.c
index 7f616c9..38dc598 100644 (file)
--- a/lustre/ptlrpc/sec.c
+++ b/lustre/ptlrpc/sec.c
@@ -114,10 +114,9 @@ static
 struct ptlrpc_sec_policy *sptlrpc_wireflavor2policy(__u32 flavor)
 {
        static DEFINE_MUTEX(load_mutex);
-       static atomic_t           loaded = ATOMIC_INIT(0);
        struct ptlrpc_sec_policy *policy;
-       __u16                     number = SPTLRPC_FLVR_POLICY(flavor);
-       __u16                     flag = 0;
+       __u16 number = SPTLRPC_FLVR_POLICY(flavor);
+       int rc;
 
        if (number >= SPTLRPC_POLICY_MAX)
                return NULL;
@@ -127,25 +126,26 @@ struct ptlrpc_sec_policy *sptlrpc_wireflavor2policy(__u32 flavor)
                policy = policies[number];
                if (policy && !try_module_get(policy->sp_owner))
                        policy = NULL;
-               if (policy == NULL)
-                       flag = atomic_read(&loaded);
                read_unlock(&policy_lock);
 
-               if (policy != NULL || flag != 0 ||
-                   number != SPTLRPC_POLICY_GSS)
+               if (policy != NULL || number != SPTLRPC_POLICY_GSS)
                        break;
 
-               /* try to load gss module, once */
+               /* try to load gss module, happens only if policy at index
+                * SPTLRPC_POLICY_GSS is not already referenced in
+                * global array policies[]
+                */
                mutex_lock(&load_mutex);
-               if (atomic_read(&loaded) == 0) {
-                       if (request_module("ptlrpc_gss") == 0)
-                               CDEBUG(D_SEC,
-                                      "module ptlrpc_gss loaded on demand\n");
-                       else
-                               CERROR("Unable to load module ptlrpc_gss\n");
-
-                       atomic_set(&loaded, 1);
-               }
+               /* The fact that request_module() returns 0 does not guarantee
+                * the module has done its job. So we must check that the
+                * requested policy is now available. This is done by checking
+                * again for policies[number] in the loop.
+                */
+               rc = request_module("ptlrpc_gss");
+               if (rc == 0)
+                       CDEBUG(D_SEC, "module ptlrpc_gss loaded on demand\n");
+               else
+                       CERROR("Unable to load module ptlrpc_gss: rc %d\n", rc);
                mutex_unlock(&load_mutex);
        }