treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index c3daf0a..cdaab30 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -239,7 +239,7 @@ void __init arch_init_ideal_nops(void)
 			return;
 		}
 
-		/* fall through */
+		fallthrough;
 
 	default:
 #ifdef CONFIG_X86_64
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 21325a4a..779a89e 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -800,7 +800,7 @@ static int irq_polarity(int idx)
 		return IOAPIC_POL_HIGH;
 	case MP_IRQPOL_RESERVED:
 		pr_warn("IOAPIC: Invalid polarity: 2, defaulting to low\n");
-		/* fall through */
+		fallthrough;
 	case MP_IRQPOL_ACTIVE_LOW:
 	default: /* Pointless default required due to do gcc stupidity */
 		return IOAPIC_POL_LOW;
@@ -848,7 +848,7 @@ static int irq_trigger(int idx)
 		return IOAPIC_EDGE;
 	case MP_IRQTRIG_RESERVED:
 		pr_warn("IOAPIC: Invalid trigger mode 2 defaulting to level\n");
-		/* fall through */
+		fallthrough;
 	case MP_IRQTRIG_LEVEL:
 	default: /* Pointless default required due to do gcc stupidity */
 		return IOAPIC_LEVEL;
diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
index 7bda71d..99ee61c 100644
--- a/arch/x86/kernel/apic/probe_32.c
+++ b/arch/x86/kernel/apic/probe_32.c
@@ -149,7 +149,7 @@ void __init default_setup_apic_routing(void)
 				break;
 			}
 			/* P4 and above */
-			/* fall through */
+			fallthrough;
 		case X86_VENDOR_HYGON:
 		case X86_VENDOR_AMD:
 			def_to_bigsmp = 1;
diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index c7503be..57074cf 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -248,7 +248,7 @@ amd_cpuid4(int leaf, union _cpuid4_leaf_eax *eax,
 	switch (leaf) {
 	case 1:
 		l1 = &l1i;
-		/* fall through */
+		fallthrough;
 	case 0:
 		if (!l1->val)
 			return;
diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 7843ab3..3a44346 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -199,7 +199,7 @@ static int raise_local(void)
 			 * calling irq_enter, but the necessary
 			 * machinery isn't exported currently.
 			 */
-			/*FALL THROUGH*/
+			fallthrough;
 		case MCJ_CTX_PROCESS:
 			raise_exception(m, NULL);
 			break;
diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
index d8f9230..abe9fe0 100644
--- a/arch/x86/kernel/cpu/mce/intel.c
+++ b/arch/x86/kernel/cpu/mce/intel.c
@@ -193,7 +193,7 @@ unsigned long cmci_intel_adjust_timer(unsigned long interval)
 		if (!atomic_sub_return(1, &cmci_storm_on_cpus))
 			pr_notice("CMCI storm subsided: switching to interrupt mode\n");
 
-		/* FALLTHROUGH */
+		fallthrough;
 
 	case CMCI_STORM_SUBSIDED:
 		/*
diff --git a/arch/x86/kernel/cpu/mtrr/cyrix.c b/arch/x86/kernel/cpu/mtrr/cyrix.c
index 7218280..ca67091 100644
--- a/arch/x86/kernel/cpu/mtrr/cyrix.c
+++ b/arch/x86/kernel/cpu/mtrr/cyrix.c
@@ -98,7 +98,7 @@ cyrix_get_free_region(unsigned long base, unsigned long size, int replace_reg)
 	case 7:
 		if (size < 0x40)
 			break;
-		/* Else, fall through */
+		fallthrough;
 	case 6:
 	case 5:
 	case 4:
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 8cdf29f..b98ff62 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -349,7 +349,7 @@ static int arch_build_bp_info(struct perf_event *bp,
 			hw->len = X86_BREAKPOINT_LEN_X;
 			return 0;
 		}
-		/* fall through */
+		fallthrough;
 	default:
 		return -EINVAL;
 	}
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 68acd30..c2f02f3 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -450,7 +450,7 @@ int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 		ptr = &remcomInBuffer[1];
 		if (kgdb_hex2long(&ptr, &addr))
 			linux_regs->ip = addr;
-		/* fall through */
+		fallthrough;
 	case 'D':
 	case 'k':
 		/* clear the trace bit */
@@ -539,7 +539,7 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 			 * a system call which should be ignored
 			 */
 			return NOTIFY_DONE;
-		/* fall through */
+		fallthrough;
 	default:
 		if (user_mode(regs))
 			return NOTIFY_DONE;
diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
index 411af4a..baa2109 100644
--- a/arch/x86/kernel/mpparse.c
+++ b/arch/x86/kernel/mpparse.c
@@ -312,7 +312,7 @@ static void __init construct_default_ioirq_mptable(int mpc_default_type)
 		case 2:
 			if (i == 0 || i == 13)
 				continue;	/* IRQ0 & IRQ13 not connected */
-			/* fall through */
+			fallthrough;
 		default:
 			if (i == 2)
 				continue;	/* IRQ2 is never connected */
@@ -356,7 +356,7 @@ static void __init construct_ioapic_table(int mpc_default_type)
 	default:
 		pr_err("???\nUnknown standard configuration %d\n",
 		       mpc_default_type);
-		/* fall through */
+		fallthrough;
 	case 1:
 	case 5:
 		memcpy(bus.bustype, "ISA   ", 6);
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 5679aa3..e7537c5 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -204,7 +204,7 @@ static int set_segment_reg(struct task_struct *task,
 	case offsetof(struct user_regs_struct, ss):
 		if (unlikely(value == 0))
 			return -EIO;
-		/* Else, fall through */
+		fallthrough;
 
 	default:
 		*pt_regs_access(task_pt_regs(task), offset) = value;
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 0ec7ced..a515e2d 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -654,7 +654,7 @@ static void native_machine_emergency_restart(void)
 
 		case BOOT_CF9_FORCE:
 			port_cf9_safe = true;
-			/* Fall through */
+			fallthrough;
 
 		case BOOT_CF9_SAFE:
 			if (port_cf9_safe) {
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index d5fa494..be0d7d4 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -726,7 +726,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 				regs->ax = -EINTR;
 				break;
 			}
-		/* fallthrough */
+			fallthrough;
 		case -ERESTARTNOINTR:
 			regs->ax = regs->orig_ax;
 			regs->ip -= 2;
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 15e5aad..3fdaa04 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -735,7 +735,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
 		 * OPCODE1() of the "short" jmp which checks the same condition.
 		 */
 		opc1 = OPCODE2(insn) - 0x10;
-		/* fall through */
+		fallthrough;
 	default:
 		if (!is_cond_jmp_opcode(opc1))
 			return -ENOSYS;
@@ -892,7 +892,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
 			fix_ip_or_call = 0;
 			break;
 		}
-		/* fall through */
+		fallthrough;
 	default:
 		riprel_analyze(auprobe, &insn);
 	}