LU-15759 libcfs: debugfs file_operation should have an owner

If debugfs a file is open when unloading the libcfs/lnet module, it
produces a kernel Oops (debugfs file_operations callbacks no longer
exist).

Crash generated with routerstat (/sys/kernel/debug/lnet/stats):
[ 1449.750396] IP: [<ffffffffab24e093>] SyS_lseek+0x83/0x100
[ 1449.750412] PGD 9fa14067 PUD 9fa16067 PMD d4e5d067 PTE 0
[ 1449.750428] Oops: 0000 [#1] SMP
[ 1449.750883]  [<ffffffffab7aaf92>] system_call_fastpath+0x25/0x2a
[ 1449.750897]  [<ffffffffab7aaed5>] ?
system_call_after_swapgs+0xa2/0x13a

This patch adds an owner to debugfs file_operation for libcfs and
lnet_router entries (/sys/kernel/debug/lnet/*).

The following behavior is expected:
$ modprobe lustre
$ routerstat 10 > /dev/null &
$ lustre_rmmod
rmmod: ERROR: Module lnet is in use
Can't read statfile (ENODEV)
[1]+  Exit 1                  routerstat 10 > /dev/null
$ lustre_rmmod

Note that the allocated 'struct file_operations' cannot be freed until
the module_exit() function is called, as files could still be open
until then.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia0920313e0c2a4b6cdc875fed08221e174a12a73
Reviewed-on: https://review.whamcloud.com/47335
Reviewed-by: Etienne AUJAMES <eaujames@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/libcfs/include/libcfs/libcfs.h b/libcfs/include/libcfs/libcfs.h
index 601ebfe..50ad978 100644 (file)
--- a/libcfs/include/libcfs/libcfs.h
+++ b/libcfs/include/libcfs/libcfs.h
@@ -84,8 +84,10 @@ int libcfs_ioctl_data_adjust(struct libcfs_ioctl_data *data);
 
 extern struct workqueue_struct *cfs_rehash_wq;
 
-void lnet_insert_debugfs(struct ctl_table *table);
+void lnet_insert_debugfs(struct ctl_table *table, struct module *mod,
+                        void **statep);
 void lnet_remove_debugfs(struct ctl_table *table);
+void lnet_debugfs_fini(void **statep);
 
 /* helper for sysctl handlers */
 int debugfs_doint(struct ctl_table *table, int write,

diff --git a/libcfs/libcfs/module.c b/libcfs/libcfs/module.c
index 82a75a7..3345203 100644 (file)
--- a/libcfs/libcfs/module.c
+++ b/libcfs/libcfs/module.c
@@ -768,19 +768,22 @@ static const struct file_operations lnet_debugfs_file_operations_wo = {
        .llseek         = default_llseek,
 };
 
-static const struct file_operations *lnet_debugfs_fops_select(umode_t mode)
+static const struct file_operations *lnet_debugfs_fops_select(
+       umode_t mode, const struct file_operations state[3])
 {
        if (!(mode & S_IWUGO))
-               return &lnet_debugfs_file_operations_ro;
+               return &state[0];
 
        if (!(mode & S_IRUGO))
-               return &lnet_debugfs_file_operations_wo;
+               return &state[1];
 
-       return &lnet_debugfs_file_operations_rw;
+       return &state[2];
 }
 
-void lnet_insert_debugfs(struct ctl_table *table)
+void lnet_insert_debugfs(struct ctl_table *table, struct module *mod,
+                        void **statep)
 {
+       struct file_operations *state = *statep;
        if (!lnet_debugfs_root)
                lnet_debugfs_root = debugfs_create_dir("lnet", NULL);
 
@@ -788,16 +791,37 @@ void lnet_insert_debugfs(struct ctl_table *table)
        if (IS_ERR_OR_NULL(lnet_debugfs_root))
                return;
 
+       if (!state) {
+               state = kmalloc(3 * sizeof(*state), GFP_KERNEL);
+               if (!state)
+                       return;
+               state[0] = lnet_debugfs_file_operations_ro;
+               state[0].owner = mod;
+               state[1] = lnet_debugfs_file_operations_wo;
+               state[1].owner = mod;
+               state[2] = lnet_debugfs_file_operations_rw;
+               state[2].owner = mod;
+               *statep = state;
+       }
+
        /* We don't save the dentry returned in next two calls, because
         * we don't call debugfs_remove() but rather remove_recursive()
         */
        for (; table && table->procname; table++)
                debugfs_create_file(table->procname, table->mode,
                                    lnet_debugfs_root, table,
-                                   lnet_debugfs_fops_select(table->mode));
+                                   lnet_debugfs_fops_select(table->mode,
+                                                            (const struct file_operations *)state));
 }
 EXPORT_SYMBOL_GPL(lnet_insert_debugfs);
 
+void lnet_debugfs_fini(void **state)
+{
+       kfree(*state);
+       *state = NULL;
+}
+EXPORT_SYMBOL_GPL(lnet_debugfs_fini);
+
 static void lnet_insert_debugfs_links(
                const struct lnet_debugfs_symlink_def *symlinks)
 {
@@ -819,6 +843,7 @@ void lnet_remove_debugfs(struct ctl_table *table)
 }
 EXPORT_SYMBOL_GPL(lnet_remove_debugfs);
 
+static void *debugfs_state;
 static int __init libcfs_init(void)
 {
        int rc;
@@ -865,7 +890,7 @@ static int __init libcfs_init(void)
                goto cleanup_wi;
        }
 
-       lnet_insert_debugfs(lnet_table);
+       lnet_insert_debugfs(lnet_table, THIS_MODULE, &debugfs_state);
        if (!IS_ERR_OR_NULL(lnet_debugfs_root))
                lnet_insert_debugfs_links(lnet_debugfs_symlinks);
 
@@ -898,6 +923,8 @@ static void __exit libcfs_exit(void)
        debugfs_remove_recursive(lnet_debugfs_root);
        lnet_debugfs_root = NULL;
 
+       lnet_debugfs_fini(&debugfs_state);
+
        CDEBUG(D_MALLOC, "before Portals cleanup: kmem %lld\n",
               libcfs_kmem_read());
 

diff --git a/lnet/include/lnet/lib-lnet.h b/lnet/include/lnet/lib-lnet.h
index e3b8428..aa3e10e 100644 (file)
--- a/lnet/include/lnet/lib-lnet.h
+++ b/lnet/include/lnet/lib-lnet.h
@@ -599,6 +599,7 @@ struct lnet_net *lnet_get_net_locked(__u32 net_id);
 
 int lnet_lib_init(void);
 void lnet_lib_exit(void);
+void lnet_router_exit(void);
 
 extern unsigned int lnet_response_tracking;
 extern unsigned lnet_transaction_timeout;

diff --git a/lnet/lnet/module.c b/lnet/lnet/module.c
index e4fe3f8..fba972c 100644 (file)
--- a/lnet/lnet/module.c
+++ b/lnet/lnet/module.c
@@ -265,6 +265,7 @@ static void __exit lnet_exit(void)
                                                &lnet_ioctl_handler);
        LASSERT(rc == 0);
 
+       lnet_router_exit();
        lnet_lib_exit();
 }
 

diff --git a/lnet/lnet/router_proc.c b/lnet/lnet/router_proc.c
index 9268914..af40833 100644 (file)
--- a/lnet/lnet/router_proc.c
+++ b/lnet/lnet/router_proc.c
@@ -891,12 +891,19 @@ static struct ctl_table lnet_table[] = {
        { .procname = NULL }
 };
 
+static void *debugfs_state;
+
 void lnet_router_debugfs_init(void)
 {
-       lnet_insert_debugfs(lnet_table);
+       lnet_insert_debugfs(lnet_table, THIS_MODULE,
+                           &debugfs_state);
 }
 
 void lnet_router_debugfs_fini(void)
 {
        lnet_remove_debugfs(lnet_table);
 }
+void lnet_router_exit(void)
+{
+       lnet_debugfs_fini(&debugfs_state);
+}