[CIFS] Use the kthread_ API instead of opencoding lots of hairy code for kernel thread creation and teardown.

It does not move the cifsd thread handling to kthread due to problems
found in testing with wakeup of threads blocked in the socket peek api,
but the other cifs kernel threads now use kthread.
Also cleanup cifs_init to properly unwind when thread creation fails.

Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/cifsfs.c

···
 #include <linux/vfs.h>
 #include <linux/mempool.h>
 #include <linux/delay.h>
+#include <linux/kthread.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
 #define DECLARE_GLOBALS_HERE
···
 unsigned int cifs_max_pending = CIFS_MAX_REQ;
 module_param(cifs_max_pending, int, 0);
 MODULE_PARM_DESC(cifs_max_pending,"Simultaneous requests to server. Default: 50 Range: 2 to 256");
-
-static DECLARE_COMPLETION(cifs_oplock_exited);
-static DECLARE_COMPLETION(cifs_dnotify_exited);
 
 extern mempool_t *cifs_sm_req_poolp;
 extern mempool_t *cifs_req_poolp;
···
 	__u16  netfid;
 	int rc;
 
-	daemonize("cifsoplockd");
-	allow_signal(SIGTERM);
-
-	oplockThread = current;
 	do {
 		if (try_to_freeze()) 
 			continue;
···
 			set_current_state(TASK_INTERRUPTIBLE);
 			schedule_timeout(1);  /* yield in case q were corrupt */
 		}
-	} while(!signal_pending(current));
-	oplockThread = NULL;
-	complete_and_exit (&cifs_oplock_exited, 0);
+	} while (!kthread_should_stop());
+
+	return 0;
 }
 
 static int cifs_dnotify_thread(void * dummyarg)
···
 	struct list_head *tmp;
 	struct cifsSesInfo *ses;
 
-	daemonize("cifsdnotifyd");
-	allow_signal(SIGTERM);
-
-	dnotifyThread = current;
 	do {
 		if(try_to_freeze())
 			continue;
···
 				wake_up_all(&ses->server->response_q);
 		}
 		read_unlock(&GlobalSMBSeslock);
-	} while(!signal_pending(current));
-	complete_and_exit (&cifs_dnotify_exited, 0);
+	} while (!kthread_should_stop());
+
+	return 0;
 }
 
 static int __init
···
 	}
 
 	rc = cifs_init_inodecache();
-	if (!rc) {
-		rc = cifs_init_mids();
-		if (!rc) {
-			rc = cifs_init_request_bufs();
-			if (!rc) {
-				rc = register_filesystem(&cifs_fs_type);
-				if (!rc) {                
-					rc = (int)kernel_thread(cifs_oplock_thread, NULL, 
-						CLONE_FS | CLONE_FILES | CLONE_VM);
-					if(rc > 0) {
-						rc = (int)kernel_thread(cifs_dnotify_thread, NULL,
-							CLONE_FS | CLONE_FILES | CLONE_VM);
-						if(rc > 0)
-							return 0;
-						else
-							cERROR(1,("error %d create dnotify thread", rc));
-					} else {
-						cERROR(1,("error %d create oplock thread",rc));
-					}
-				}
-				cifs_destroy_request_bufs();
-			}
-			cifs_destroy_mids();
-		}
-		cifs_destroy_inodecache();
+	if (rc)
+		goto out_clean_proc;
+
+	rc = cifs_init_mids();
+	if (rc)
+		goto out_destroy_inodecache;
+
+	rc = cifs_init_request_bufs();
+	if (rc)
+		goto out_destroy_mids;
+
+	rc = register_filesystem(&cifs_fs_type);
+	if (rc)
+		goto out_destroy_request_bufs;
+
+	oplockThread = kthread_run(cifs_oplock_thread, NULL, "cifsoplockd");
+	if (IS_ERR(oplockThread)) {
+		rc = PTR_ERR(oplockThread);
+		cERROR(1,("error %d create oplock thread", rc));
+		goto out_unregister_filesystem;
 	}
+
+	dnotifyThread = kthread_run(cifs_dnotify_thread, NULL, "cifsdnotifyd");
+	if (IS_ERR(dnotifyThread)) {
+		rc = PTR_ERR(dnotifyThread);
+		cERROR(1,("error %d create dnotify thread", rc));
+		goto out_stop_oplock_thread;
+	}
+
+	return 0;
+
+ out_stop_oplock_thread:
+	kthread_stop(oplockThread);
+ out_unregister_filesystem:
+	unregister_filesystem(&cifs_fs_type);
+ out_destroy_request_bufs:
+	cifs_destroy_request_bufs();
+ out_destroy_mids:
+	cifs_destroy_mids();
+ out_destroy_inodecache:
+	cifs_destroy_inodecache();
+ out_clean_proc:
 #ifdef CONFIG_PROC_FS
 	cifs_proc_clean();
 #endif
···
 	cifs_destroy_inodecache();
 	cifs_destroy_mids();
 	cifs_destroy_request_bufs();
-	if(oplockThread) {
-		send_sig(SIGTERM, oplockThread, 1);
-		wait_for_completion(&cifs_oplock_exited);
-	}
-	if(dnotifyThread) {
-		send_sig(SIGTERM, dnotifyThread, 1);
-		wait_for_completion(&cifs_dnotify_exited);
-	}
+	kthread_stop(oplockThread);
+	kthread_stop(dnotifyThread);
 }
 
 MODULE_AUTHOR("Steve French <[e-mail]>");