LU-9679 llite: fix possible race with module unload.

lustre_fill_super() calls client_fill_super() without holding a
reference to the module containing client_fill_super.  If that
module is unloaded at a bad time, this can crash.

To be able to get a reference to the module using
try_get_module(), we need a pointer to the module.

So replace
  lustre_register_client_fill_super() and
  lustre_register_kill_super_cb()
with a single
  lustre_register_super_ops()
which also passed a module pointer.

Then use a spinlock to ensure the module pointer isn't removed
while try_module_get() is running, and use try_module_get() to
ensure we have a reference before calling client_fill_super().

Now that we take the reference to the module before calling
luster_fill_super(), we don't need to take one inside
lustre_fill_super().

Linux-commit: d487fe31f49e78f3cdd826923bf0c340a839ffd8

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I9474622f2a253d9882eae3f0578c50782dd11ad4
Reviewed-on: https://review.whamcloud.com/37020
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/include/lustre_disk.h b/lustre/include/lustre_disk.h
index a809f4b..385cc1e 100644 (file)
--- a/lustre/include/lustre_disk.h
+++ b/lustre/include/lustre_disk.h
@@ -349,8 +349,9 @@ int lustre_start_mgc(struct super_block *sb);
 int server_name2fsname(const char *svname, char *fsname, const char **endptr);
 void obdname2fsname(const char *tgt, char *fsname, size_t fslen);
 
 int server_name2fsname(const char *svname, char *fsname, const char **endptr);
 void obdname2fsname(const char *tgt, char *fsname, size_t fslen);
 

-void lustre_register_client_fill_super(int (*cfs)(struct super_block *sb));
-void lustre_register_kill_super_cb(void (*cfs)(struct super_block *sb));
+void lustre_register_super_ops(struct module *mod,
+                              int (*cfs)(struct super_block *sb),
+                              void (*ksc)(struct super_block *sb));

 int lustre_common_put_super(struct super_block *sb);
 
 int mgc_fsname2resid(char *fsname, struct ldlm_res_id *res_id, int type);
 int lustre_common_put_super(struct super_block *sb);
 
 int mgc_fsname2resid(char *fsname, struct ldlm_res_id *res_id, int type);

diff --git a/lustre/llite/llite_lib.c b/lustre/llite/llite_lib.c
index f92cd7d..69a5062 100644 (file)
--- a/lustre/llite/llite_lib.c
+++ b/lustre/llite/llite_lib.c
@@ -1075,8 +1075,6 @@ int ll_fill_super(struct super_block *sb)
        CDEBUG(D_VFSTRACE, "VFS Op: cfg_instance %s-%016lx (sb %p)\n",
               profilenm, cfg_instance, sb);
 
        CDEBUG(D_VFSTRACE, "VFS Op: cfg_instance %s-%016lx (sb %p)\n",
               profilenm, cfg_instance, sb);
 

-       try_module_get(THIS_MODULE);
-

        OBD_ALLOC_PTR(cfg);
        if (cfg == NULL)
                GOTO(out_free_cfg, err = -ENOMEM);
        OBD_ALLOC_PTR(cfg);
        if (cfg == NULL)
                GOTO(out_free_cfg, err = -ENOMEM);

diff --git a/lustre/llite/super25.c b/lustre/llite/super25.c
index 2a510ef..befd246 100644 (file)
--- a/lustre/llite/super25.c
+++ b/lustre/llite/super25.c
@@ -149,8 +149,7 @@ static int __init lustre_init(void)
        if (rc != 0)
                GOTO(out_inode_fini_env, rc);
 
        if (rc != 0)
                GOTO(out_inode_fini_env, rc);
 

-       lustre_register_client_fill_super(ll_fill_super);
-       lustre_register_kill_super_cb(ll_kill_super);
+       lustre_register_super_ops(THIS_MODULE, ll_fill_super, ll_kill_super);

 
        RETURN(0);
 
 
        RETURN(0);
 


@@ -169,8 +168,7 @@ out_cache:
 
 static void __exit lustre_exit(void)
 {
 
 static void __exit lustre_exit(void)
 {

-       lustre_register_client_fill_super(NULL);
-       lustre_register_kill_super_cb(NULL);
+       lustre_register_super_ops(NULL, NULL, NULL);

 
        llite_tunables_unregister();
 
 
        llite_tunables_unregister();
 

diff --git a/lustre/obdclass/obd_mount.c b/lustre/obdclass/obd_mount.c
index 538efea..b9c14d2 100644 (file)
--- a/lustre/obdclass/obd_mount.c
+++ b/lustre/obdclass/obd_mount.c
@@ -50,6 +50,8 @@
 #include <lustre_disk.h>
 #include <uapi/linux/lustre/lustre_param.h>
 
 #include <lustre_disk.h>
 #include <uapi/linux/lustre/lustre_param.h>
 

+static DEFINE_SPINLOCK(client_lock);
+static struct module *client_mod;

 static int (*client_fill_super)(struct super_block *sb);
 
 static void (*kill_super_cb)(struct super_block *sb);
 static int (*client_fill_super)(struct super_block *sb);
 
 static void (*kill_super_cb)(struct super_block *sb);


@@ -1623,10 +1625,16 @@ static int lustre_fill_super(struct super_block *sb, void *lmd2_data,
        }
 
        if (lmd_is_client(lmd)) {
        }
 
        if (lmd_is_client(lmd)) {

+               bool have_client = false;
+

                CDEBUG(D_MOUNT, "Mounting client %s\n", lmd->lmd_profile);
                CDEBUG(D_MOUNT, "Mounting client %s\n", lmd->lmd_profile);

-               if (client_fill_super == NULL)
+               if (!client_fill_super)

                        request_module("lustre");
                        request_module("lustre");

-               if (client_fill_super == NULL) {
+               spin_lock(&client_lock);
+               if (client_fill_super && try_module_get(client_mod))
+                       have_client = true;
+               spin_unlock(&client_lock);
+               if (!have_client) {

                        LCONSOLE_ERROR_MSG(0x165,
                                           "Nothing registered for client mount! Is the 'lustre' module loaded?\n");
                        lustre_put_lsi(sb);
                        LCONSOLE_ERROR_MSG(0x165,
                                           "Nothing registered for client mount! Is the 'lustre' module loaded?\n");
                        lustre_put_lsi(sb);


@@ -1640,7 +1648,9 @@ static int lustre_fill_super(struct super_block *sb, void *lmd2_data,
                        /* Connect and start */
                        /* (should always be ll_fill_super) */
                        rc = (*client_fill_super)(sb);
                        /* Connect and start */
                        /* (should always be ll_fill_super) */
                        rc = (*client_fill_super)(sb);

-                       /* c_f_s will call lustre_common_put_super on failure */
+                       /* c_f_s will call lustre_common_put_super on failure,
+                        * which takes care of the module reference.
+                        */

                }
        } else {
 #ifdef HAVE_SERVER_SUPPORT
                }
        } else {
 #ifdef HAVE_SERVER_SUPPORT


@@ -1680,17 +1690,17 @@ out:
  * We can't call ll_fill_super by name because it lives in a module that
  * must be loaded after this one.
  */
  * We can't call ll_fill_super by name because it lives in a module that
  * must be loaded after this one.
  */

-void lustre_register_client_fill_super(int (*cfs)(struct super_block *sb))
+void lustre_register_super_ops(struct module *mod,
+                              int (*cfs)(struct super_block *sb),
+                              void (*ksc)(struct super_block *sb))

 {
 {

+       spin_lock(&client_lock);
+       client_mod = mod;

        client_fill_super = cfs;
        client_fill_super = cfs;

+       kill_super_cb = ksc;
+       spin_unlock(&client_lock);

 }
 }

-EXPORT_SYMBOL(lustre_register_client_fill_super);
-
-void lustre_register_kill_super_cb(void (*cfs)(struct super_block *sb))
-{
-       kill_super_cb = cfs;
-}
-EXPORT_SYMBOL(lustre_register_kill_super_cb);
+EXPORT_SYMBOL(lustre_register_super_ops);

 
 /***************** FS registration ******************/
 #ifdef HAVE_FSTYPE_MOUNT
 
 /***************** FS registration ******************/
 #ifdef HAVE_FSTYPE_MOUNT