smb3: add dynamic tracepoints for shutdown ioctl

For debugging an umount failure in xfstests generic/043 generic/044 in some
configurations, we needed more information on the shutdown ioctl which
was suspected of being related to the cause, so tracepoints are added
in this patch e.g.

  "trace-cmd record -e smb3_shutdown_enter -e smb3_shutdown_done -e smb3_shutdown_err"

Sample output:
  godown-47084   [011] .....  3313.756965: smb3_shutdown_enter: flags=0x1 tid=0x733b3e75
  godown-47084   [011] .....  3313.756968: smb3_shutdown_done: flags=0x1 tid=0x733b3e75
Tested-by: Anthony Nandaa (Microsoft) <profnandaa@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/ioctl.c

@@ -170,7 +170,10 @@ static long smb_mnt_get_fsinfo(unsigned int xid, struct cifs_tcon *tcon,
 static int cifs_shutdown(struct super_block *sb, unsigned long arg)
 {
 	struct cifs_sb_info *sbi = CIFS_SB(sb);
+	struct tcon_link *tlink;
+	struct cifs_tcon *tcon;
 	__u32 flags;
+	int rc;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -178,14 +181,21 @@ static int cifs_shutdown(struct super_block *sb, unsigned long arg)
 	if (get_user(flags, (__u32 __user *)arg))
 		return -EFAULT;
 
-	if (flags > CIFS_GOING_FLAGS_NOLOGFLUSH)
-		return -EINVAL;
+	tlink = cifs_sb_tlink(sbi);
+	if (IS_ERR(tlink))
+		return PTR_ERR(tlink);
+	tcon = tlink_tcon(tlink);
+
+	trace_smb3_shutdown_enter(flags, tcon->tid);
+	if (flags > CIFS_GOING_FLAGS_NOLOGFLUSH) {
+		rc = -EINVAL;
+		goto shutdown_out_err;
+	}
 
 	if (cifs_forced_shutdown(sbi))
-		return 0;
+		goto shutdown_good;
 
 	cifs_dbg(VFS, "shut down requested (%d)", flags);
-/*	trace_cifs_shutdown(sb, flags);*/
 
 	/*
 	 * see:
@@ -201,7 +211,8 @@ static int cifs_shutdown(struct super_block *sb, unsigned long arg)
 	 */
 	case CIFS_GOING_FLAGS_DEFAULT:
 		cifs_dbg(FYI, "shutdown with default flag not supported\n");
-		return -EINVAL;
+		rc = -EINVAL;
+		goto shutdown_out_err;
 	/*
 	 * FLAGS_LOGFLUSH is easy since it asks to write out metadata (not
 	 * data) but metadata writes are not cached on the client, so can treat
@@ -210,11 +221,18 @@ static int cifs_shutdown(struct super_block *sb, unsigned long arg)
 	case CIFS_GOING_FLAGS_LOGFLUSH:
 	case CIFS_GOING_FLAGS_NOLOGFLUSH:
 		sbi->mnt_cifs_flags |= CIFS_MOUNT_SHUTDOWN;
-		return 0;
+		goto shutdown_good;
 	default:
-		return -EINVAL;
+		rc = -EINVAL;
+		goto shutdown_out_err;
 	}
+
+shutdown_good:
+	trace_smb3_shutdown_done(flags, tcon->tid);
 	return 0;
+shutdown_out_err:
+	trace_smb3_shutdown_err(rc, flags, tcon->tid);
+	return rc;
 }
 
 static int cifs_dump_full_key(struct cifs_tcon *tcon, struct smb3_full_key_debug_info __user *in)

fs/smb/client/trace.h

@@ -1400,9 +1400,58 @@ DEFINE_EVENT(smb3_ioctl_class, smb3_##name,  \
 
 DEFINE_SMB3_IOCTL_EVENT(ioctl);
 
+DECLARE_EVENT_CLASS(smb3_shutdown_class,
+	TP_PROTO(__u32 flags,
+		__u32 tid),
+	TP_ARGS(flags, tid),
+	TP_STRUCT__entry(
+		__field(__u32, flags)
+		__field(__u32, tid)
+	),
+	TP_fast_assign(
+		__entry->flags = flags;
+		__entry->tid = tid;
+	),
+	TP_printk("flags=0x%x tid=0x%x",
+		  __entry->flags, __entry->tid)
+)
+
+#define DEFINE_SMB3_SHUTDOWN_EVENT(name)        \
+DEFINE_EVENT(smb3_shutdown_class, smb3_##name,  \
+	TP_PROTO(__u32 flags,		     \
+		__u32 tid),		     \
+	TP_ARGS(flags, tid))
+
+DEFINE_SMB3_SHUTDOWN_EVENT(shutdown_enter);
+DEFINE_SMB3_SHUTDOWN_EVENT(shutdown_done);
 
+DECLARE_EVENT_CLASS(smb3_shutdown_err_class,
+	TP_PROTO(int rc,
+		__u32 flags,
+		__u32 tid),
+	TP_ARGS(rc, flags, tid),
+	TP_STRUCT__entry(
+		__field(int, rc)
+		__field(__u32, flags)
+		__field(__u32, tid)
+	),
+	TP_fast_assign(
+		__entry->rc = rc;
+		__entry->flags = flags;
+		__entry->tid = tid;
+	),
+	TP_printk("rc=%d flags=0x%x tid=0x%x",
+		__entry->rc, __entry->flags, __entry->tid)
+)
 
+#define DEFINE_SMB3_SHUTDOWN_ERR_EVENT(name)        \
+DEFINE_EVENT(smb3_shutdown_err_class, smb3_##name,  \
+	TP_PROTO(int rc,		     \
+		__u32 flags,		     \
+		__u32 tid),		     \
+	TP_ARGS(rc, flags, tid))
 
+DEFINE_SMB3_SHUTDOWN_ERR_EVENT(shutdown_err);
 
 DECLARE_EVENT_CLASS(smb3_credit_class,
 	TP_PROTO(__u64	currmid,