ftrace: new continue entry - separate out from trace_entry

Some tracers will need to work with more than one entry. In order to do this
the trace_entry structure was split into two fields. One for the start of
all entries, and one to continue an existing entry.

The trace_entry structure now has a "field" entry that consists of the previous
content of the trace_entry, and a "cont" entry that is just a string buffer
the size of the "field" entry.

Thanks to Andrew Morton for suggesting this idea.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 160 insertions, 136 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8f3fb3db61c3..76dfe6d2466c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -817,10 +817,11 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags)
 
         pc = preempt_count();
 
-        entry->preempt_count    = pc & 0xff;
-        entry->pid              = (tsk) ? tsk->pid : 0;
-        entry->t                = ftrace_now(raw_smp_processor_id());
-        entry->flags = (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
+        entry->field.preempt_count      = pc & 0xff;
+        entry->field.pid                = (tsk) ? tsk->pid : 0;
+        entry->field.t                  = ftrace_now(raw_smp_processor_id());
+        entry->field.flags =
+                (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
                 ((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
                 ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
                 (need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
@@ -835,11 +836,11 @@ trace_function(struct trace_array *tr, struct trace_array_cpu *data,
 
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&data->lock);
-        entry                   = tracing_get_trace_entry(tr, data);
+        entry                           = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, flags);
-        entry->type             = TRACE_FN;
-        entry->fn.ip            = ip;
-        entry->fn.parent_ip     = parent_ip;
+        entry->type                     = TRACE_FN;
+        entry->field.fn.ip              = ip;
+        entry->field.fn.parent_ip       = parent_ip;
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
 }
@@ -862,10 +863,10 @@ void __trace_mmiotrace_rw(struct trace_array *tr, struct trace_array_cpu *data,
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&data->lock);
 
-        entry                   = tracing_get_trace_entry(tr, data);
+        entry                           = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, 0);
-        entry->type             = TRACE_MMIO_RW;
-        entry->mmiorw           = *rw;
+        entry->type                     = TRACE_MMIO_RW;
+        entry->field.mmiorw             = *rw;
 
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
@@ -882,10 +883,10 @@ void __trace_mmiotrace_map(struct trace_array *tr, struct trace_array_cpu *data,
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&data->lock);
 
-        entry                   = tracing_get_trace_entry(tr, data);
+        entry                           = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, 0);
-        entry->type             = TRACE_MMIO_MAP;
-        entry->mmiomap          = *map;
+        entry->type                     = TRACE_MMIO_MAP;
+        entry->field.mmiomap            = *map;
 
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
@@ -909,12 +910,12 @@ void __trace_stack(struct trace_array *tr,
         tracing_generic_entry_update(entry, flags);
         entry->type             = TRACE_STACK;
 
-        memset(&entry->stack, 0, sizeof(entry->stack));
+        memset(&entry->field.stack, 0, sizeof(entry->field.stack));
 
         trace.nr_entries        = 0;
         trace.max_entries       = FTRACE_STACK_ENTRIES;
         trace.skip              = skip;
-        trace.entries           = entry->stack.caller;
+        trace.entries           = entry->field.stack.caller;
 
         save_stack_trace(&trace);
 }
@@ -930,12 +931,12 @@ __trace_special(void *__tr, void *__data,
 
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&data->lock);
-        entry                   = tracing_get_trace_entry(tr, data);
+        entry                           = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, 0);
-        entry->type             = TRACE_SPECIAL;
-        entry->special.arg1     = arg1;
-        entry->special.arg2     = arg2;
-        entry->special.arg3     = arg3;
+        entry->type                     = TRACE_SPECIAL;
+        entry->field.special.arg1       = arg1;
+        entry->field.special.arg2       = arg2;
+        entry->field.special.arg3       = arg3;
         __trace_stack(tr, data, irq_flags, 4);
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
@@ -955,15 +956,15 @@ tracing_sched_switch_trace(struct trace_array *tr,
 
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&data->lock);
-        entry                   = tracing_get_trace_entry(tr, data);
+        entry                           = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, flags);
-        entry->type             = TRACE_CTX;
-        entry->ctx.prev_pid     = prev->pid;
-        entry->ctx.prev_prio    = prev->prio;
-        entry->ctx.prev_state   = prev->state;
-        entry->ctx.next_pid     = next->pid;
-        entry->ctx.next_prio    = next->prio;
-        entry->ctx.next_state   = next->state;
+        entry->type                     = TRACE_CTX;
+        entry->field.ctx.prev_pid       = prev->pid;
+        entry->field.ctx.prev_prio      = prev->prio;
+        entry->field.ctx.prev_state     = prev->state;
+        entry->field.ctx.next_pid       = next->pid;
+        entry->field.ctx.next_prio      = next->prio;
+        entry->field.ctx.next_state     = next->state;
         __trace_stack(tr, data, flags, 5);
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
@@ -984,12 +985,12 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         entry                   = tracing_get_trace_entry(tr, data);
         tracing_generic_entry_update(entry, flags);
         entry->type             = TRACE_WAKE;
-        entry->ctx.prev_pid     = curr->pid;
-        entry->ctx.prev_prio    = curr->prio;
-        entry->ctx.prev_state   = curr->state;
-        entry->ctx.next_pid     = wakee->pid;
-        entry->ctx.next_prio    = wakee->prio;
-        entry->ctx.next_state   = wakee->state;
+        entry->field.ctx.prev_pid       = curr->pid;
+        entry->field.ctx.prev_prio      = curr->prio;
+        entry->field.ctx.prev_state     = curr->state;
+        entry->field.ctx.next_pid       = wakee->pid;
+        entry->field.ctx.next_prio      = wakee->prio;
+        entry->field.ctx.next_state     = wakee->state;
         __trace_stack(tr, data, flags, 6);
         __raw_spin_unlock(&data->lock);
         raw_local_irq_restore(irq_flags);
@@ -1118,7 +1119,7 @@ find_next_entry(struct trace_iterator *iter, int *ent_cpu)
                 /*
                  * Pick the entry with the smallest timestamp:
                  */
-                if (ent && (!next || ent->t < next->t)) {
+                if (ent && (!next || ent->field.t < next->field.t)) {
                         next = ent;
                         next_cpu = cpu;
                 }
@@ -1422,19 +1423,20 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 static void
 lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
 {
+        struct trace_field *field = &entry->field;
         int hardirq, softirq;
         char *comm;
 
-        comm = trace_find_cmdline(entry->pid);
+        comm = trace_find_cmdline(field->pid);
 
-        trace_seq_printf(s, "%8.8s-%-5d ", comm, entry->pid);
+        trace_seq_printf(s, "%8.8s-%-5d ", comm, field->pid);
         trace_seq_printf(s, "%d", cpu);
         trace_seq_printf(s, "%c%c",
-                        (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
-                        ((entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'));
+                        (field->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : '.',
+                        ((field->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.'));
 
-        hardirq = entry->flags & TRACE_FLAG_HARDIRQ;
-        softirq = entry->flags & TRACE_FLAG_SOFTIRQ;
+        hardirq = field->flags & TRACE_FLAG_HARDIRQ;
+        softirq = field->flags & TRACE_FLAG_SOFTIRQ;
         if (hardirq && softirq) {
                 trace_seq_putc(s, 'H');
         } else {
@@ -1448,8 +1450,8 @@ lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
                 }
         }
 
-        if (entry->preempt_count)
-                trace_seq_printf(s, "%x", entry->preempt_count);
+        if (field->preempt_count)
+                trace_seq_printf(s, "%x", field->preempt_count);
         else
                 trace_seq_puts(s, ".");
 }
@@ -1479,6 +1481,7 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         struct trace_entry *next_entry = find_next_entry(iter, NULL);
         unsigned long verbose = (trace_flags & TRACE_ITER_VERBOSE);
         struct trace_entry *entry = iter->ent;
+        struct trace_field *field = &entry->field;
         unsigned long abs_usecs;
         unsigned long rel_usecs;
         char *comm;
@@ -1488,17 +1491,17 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 
         if (!next_entry)
                 next_entry = entry;
-        rel_usecs = ns2usecs(next_entry->t - entry->t);
-        abs_usecs = ns2usecs(entry->t - iter->tr->time_start);
+        rel_usecs = ns2usecs(next_entry->field.t - entry->field.t);
+        abs_usecs = ns2usecs(entry->field.t - iter->tr->time_start);
 
         if (verbose) {
-                comm = trace_find_cmdline(entry->pid);
+                comm = trace_find_cmdline(field->pid);
                 trace_seq_printf(s, "%16s %5d %d %d %08x %08x [%08lx]"
                                  " %ld.%03ldms (+%ld.%03ldms): ",
                                  comm,
-                                 entry->pid, cpu, entry->flags,
-                                 entry->preempt_count, trace_idx,
-                                 ns2usecs(entry->t),
+                                 field->pid, cpu, field->flags,
+                                 field->preempt_count, trace_idx,
+                                 ns2usecs(field->t),
                                  abs_usecs/1000,
                                  abs_usecs % 1000, rel_usecs/1000,
                                  rel_usecs % 1000);
@@ -1508,41 +1511,42 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         }
         switch (entry->type) {
         case TRACE_FN:
-                seq_print_ip_sym(s, entry->fn.ip, sym_flags);
+                seq_print_ip_sym(s, field->fn.ip, sym_flags);
                 trace_seq_puts(s, " (");
-                if (kretprobed(entry->fn.parent_ip))
+                if (kretprobed(field->fn.parent_ip))
                         trace_seq_puts(s, KRETPROBE_MSG);
                 else
-                        seq_print_ip_sym(s, entry->fn.parent_ip, sym_flags);
+                        seq_print_ip_sym(s, field->fn.parent_ip, sym_flags);
                 trace_seq_puts(s, ")\n");
                 break;
         case TRACE_CTX:
         case TRACE_WAKE:
-                T = entry->ctx.next_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.next_state] : 'X';
+                T = field->ctx.next_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.next_state] : 'X';
 
-                state = entry->ctx.prev_state ? __ffs(entry->ctx.prev_state) + 1 : 0;
+                state = field->ctx.prev_state ?
+                        __ffs(field->ctx.prev_state) + 1 : 0;
                 S = state < sizeof(state_to_char) - 1 ? state_to_char[state] : 'X';
-                comm = trace_find_cmdline(entry->ctx.next_pid);
+                comm = trace_find_cmdline(field->ctx.next_pid);
                 trace_seq_printf(s, " %5d:%3d:%c %s %5d:%3d:%c %s\n",
-                                 entry->ctx.prev_pid,
-                                 entry->ctx.prev_prio,
+                                 field->ctx.prev_pid,
+                                 field->ctx.prev_prio,
                                  S, entry->type == TRACE_CTX ? "==>" : "  +",
-                                 entry->ctx.next_pid,
-                                 entry->ctx.next_prio,
+                                 field->ctx.next_pid,
+                                 field->ctx.next_prio,
                                  T, comm);
                 break;
         case TRACE_SPECIAL:
                 trace_seq_printf(s, "# %ld %ld %ld\n",
-                                 entry->special.arg1,
-                                 entry->special.arg2,
-                                 entry->special.arg3);
+                                 field->special.arg1,
+                                 field->special.arg2,
+                                 field->special.arg3);
                 break;
         case TRACE_STACK:
                 for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
                         if (i)
                                 trace_seq_puts(s, " <= ");
-                        seq_print_ip_sym(s, entry->stack.caller[i], sym_flags);
+                        seq_print_ip_sym(s, field->stack.caller[i], sym_flags);
                 }
                 trace_seq_puts(s, "\n");
                 break;
@@ -1557,6 +1561,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
         struct trace_seq *s = &iter->seq;
         unsigned long sym_flags = (trace_flags & TRACE_ITER_SYM_MASK);
         struct trace_entry *entry;
+        struct trace_field *field;
         unsigned long usec_rem;
         unsigned long long t;
         unsigned long secs;
@@ -1566,14 +1571,15 @@ static int print_trace_fmt(struct trace_iterator *iter)
         int i;
 
         entry = iter->ent;
+        field = &entry->field;
 
-        comm = trace_find_cmdline(iter->ent->pid);
+        comm = trace_find_cmdline(iter->ent->field.pid);
 
-        t = ns2usecs(entry->t);
+        t = ns2usecs(field->t);
         usec_rem = do_div(t, 1000000ULL);
         secs = (unsigned long)t;
 
-        ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
+        ret = trace_seq_printf(s, "%16s-%-5d ", comm, field->pid);
         if (!ret)
                 return 0;
         ret = trace_seq_printf(s, "[%02d] ", iter->cpu);
@@ -1585,18 +1591,19 @@ static int print_trace_fmt(struct trace_iterator *iter)
 
         switch (entry->type) {
         case TRACE_FN:
-                ret = seq_print_ip_sym(s, entry->fn.ip, sym_flags);
+                ret = seq_print_ip_sym(s, field->fn.ip, sym_flags);
                 if (!ret)
                         return 0;
                 if ((sym_flags & TRACE_ITER_PRINT_PARENT) &&
-                                                entry->fn.parent_ip) {
+                                                field->fn.parent_ip) {
                         ret = trace_seq_printf(s, " <-");
                         if (!ret)
                                 return 0;
-                        if (kretprobed(entry->fn.parent_ip))
+                        if (kretprobed(field->fn.parent_ip))
                                 ret = trace_seq_puts(s, KRETPROBE_MSG);
                         else
-                                ret = seq_print_ip_sym(s, entry->fn.parent_ip,
+                                ret = seq_print_ip_sym(s,
+                                                       field->fn.parent_ip,
                                                        sym_flags);
                         if (!ret)
                                 return 0;
@@ -1607,26 +1614,26 @@ static int print_trace_fmt(struct trace_iterator *iter)
                 break;
         case TRACE_CTX:
         case TRACE_WAKE:
-                S = entry->ctx.prev_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.prev_state] : 'X';
-                T = entry->ctx.next_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.next_state] : 'X';
+                S = field->ctx.prev_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.prev_state] : 'X';
+                T = field->ctx.next_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.next_state] : 'X';
                 ret = trace_seq_printf(s, " %5d:%3d:%c %s %5d:%3d:%c\n",
-                                       entry->ctx.prev_pid,
-                                       entry->ctx.prev_prio,
+                                       field->ctx.prev_pid,
+                                       field->ctx.prev_prio,
                                        S,
                                        entry->type == TRACE_CTX ? "==>" : "  +",
-                                       entry->ctx.next_pid,
-                                       entry->ctx.next_prio,
+                                       field->ctx.next_pid,
+                                       field->ctx.next_prio,
                                        T);
                 if (!ret)
                         return 0;
                 break;
         case TRACE_SPECIAL:
                 ret = trace_seq_printf(s, "# %ld %ld %ld\n",
-                                 entry->special.arg1,
-                                 entry->special.arg2,
-                                 entry->special.arg3);
+                                 field->special.arg1,
+                                 field->special.arg2,
+                                 field->special.arg3);
                 if (!ret)
                         return 0;
                 break;
@@ -1637,7 +1644,7 @@ static int print_trace_fmt(struct trace_iterator *iter)
                                 if (!ret)
                                         return 0;
                         }
-                        ret = seq_print_ip_sym(s, entry->stack.caller[i],
+                        ret = seq_print_ip_sym(s, field->stack.caller[i],
                                                sym_flags);
                         if (!ret)
                                 return 0;
@@ -1654,37 +1661,40 @@ static int print_raw_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         struct trace_entry *entry;
+        struct trace_field *field;
         int ret;
         int S, T;
 
         entry = iter->ent;
+        field = &entry->field;
 
         ret = trace_seq_printf(s, "%d %d %llu ",
-                entry->pid, iter->cpu, entry->t);
+                field->pid, iter->cpu, field->t);
         if (!ret)
                 return 0;
 
         switch (entry->type) {
         case TRACE_FN:
                 ret = trace_seq_printf(s, "%x %x\n",
-                                        entry->fn.ip, entry->fn.parent_ip);
+                                        field->fn.ip,
+                                        field->fn.parent_ip);
                 if (!ret)
                         return 0;
                 break;
         case TRACE_CTX:
         case TRACE_WAKE:
-                S = entry->ctx.prev_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.prev_state] : 'X';
-                T = entry->ctx.next_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.next_state] : 'X';
+                S = field->ctx.prev_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.prev_state] : 'X';
+                T = field->ctx.next_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.next_state] : 'X';
                 if (entry->type == TRACE_WAKE)
                         S = '+';
                 ret = trace_seq_printf(s, "%d %d %c %d %d %c\n",
-                                       entry->ctx.prev_pid,
-                                       entry->ctx.prev_prio,
+                                       field->ctx.prev_pid,
+                                       field->ctx.prev_prio,
                                        S,
-                                       entry->ctx.next_pid,
-                                       entry->ctx.next_prio,
+                                       field->ctx.next_pid,
+                                       field->ctx.next_prio,
                                        T);
                 if (!ret)
                         return 0;
@@ -1692,9 +1702,9 @@ static int print_raw_fmt(struct trace_iterator *iter)
         case TRACE_SPECIAL:
         case TRACE_STACK:
                 ret = trace_seq_printf(s, "# %ld %ld %ld\n",
-                                 entry->special.arg1,
-                                 entry->special.arg2,
-                                 entry->special.arg3);
+                                 field->special.arg1,
+                                 field->special.arg2,
+                                 field->special.arg3);
                 if (!ret)
                         return 0;
                 break;
@@ -1719,40 +1729,41 @@ static int print_hex_fmt(struct trace_iterator *iter)
         struct trace_seq *s = &iter->seq;
         unsigned char newline = '\n';
         struct trace_entry *entry;
+        struct trace_field *field;
         int S, T;
 
         entry = iter->ent;
+        field = &entry->field;
 
-        SEQ_PUT_HEX_FIELD_RET(s, entry->pid);
+        SEQ_PUT_HEX_FIELD_RET(s, field->pid);
         SEQ_PUT_HEX_FIELD_RET(s, iter->cpu);
-        SEQ_PUT_HEX_FIELD_RET(s, entry->t);
+        SEQ_PUT_HEX_FIELD_RET(s, field->t);
 
         switch (entry->type) {
         case TRACE_FN:
-                SEQ_PUT_HEX_FIELD_RET(s, entry->fn.ip);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->fn.parent_ip);
+                SEQ_PUT_HEX_FIELD_RET(s, field->fn.ip);
+                SEQ_PUT_HEX_FIELD_RET(s, field->fn.parent_ip);
                 break;
         case TRACE_CTX:
         case TRACE_WAKE:
-                S = entry->ctx.prev_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.prev_state] : 'X';
-                T = entry->ctx.next_state < sizeof(state_to_char) ?
-                        state_to_char[entry->ctx.next_state] : 'X';
+                S = field->ctx.prev_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.prev_state] : 'X';
+                T = field->ctx.next_state < sizeof(state_to_char) ?
+                        state_to_char[field->ctx.next_state] : 'X';
                 if (entry->type == TRACE_WAKE)
                         S = '+';
-                SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.prev_pid);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.prev_prio);
+                SEQ_PUT_HEX_FIELD_RET(s, field->ctx.prev_pid);
+                SEQ_PUT_HEX_FIELD_RET(s, field->ctx.prev_prio);
                 SEQ_PUT_HEX_FIELD_RET(s, S);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.next_pid);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->ctx.next_prio);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->fn.parent_ip);
+                SEQ_PUT_HEX_FIELD_RET(s, field->ctx.next_pid);
+                SEQ_PUT_HEX_FIELD_RET(s, field->ctx.next_prio);
                 SEQ_PUT_HEX_FIELD_RET(s, T);
                 break;
         case TRACE_SPECIAL:
         case TRACE_STACK:
-                SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg1);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg2);
-                SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg3);
+                SEQ_PUT_HEX_FIELD_RET(s, field->special.arg1);
+                SEQ_PUT_HEX_FIELD_RET(s, field->special.arg2);
+                SEQ_PUT_HEX_FIELD_RET(s, field->special.arg3);
                 break;
         }
         SEQ_PUT_FIELD_RET(s, newline);
@@ -1764,31 +1775,33 @@ static int print_bin_fmt(struct trace_iterator *iter)
 {
         struct trace_seq *s = &iter->seq;
         struct trace_entry *entry;
+        struct trace_field *field;
 
         entry = iter->ent;
+        field = &entry->field;
 
-        SEQ_PUT_FIELD_RET(s, entry->pid);
-        SEQ_PUT_FIELD_RET(s, entry->cpu);
-        SEQ_PUT_FIELD_RET(s, entry->t);
+        SEQ_PUT_FIELD_RET(s, field->pid);
+        SEQ_PUT_FIELD_RET(s, field->cpu);
+        SEQ_PUT_FIELD_RET(s, field->t);
 
         switch (entry->type) {
         case TRACE_FN:
-                SEQ_PUT_FIELD_RET(s, entry->fn.ip);
-                SEQ_PUT_FIELD_RET(s, entry->fn.parent_ip);
+                SEQ_PUT_FIELD_RET(s, field->fn.ip);
+                SEQ_PUT_FIELD_RET(s, field->fn.parent_ip);
                 break;
         case TRACE_CTX:
-                SEQ_PUT_FIELD_RET(s, entry->ctx.prev_pid);
-                SEQ_PUT_FIELD_RET(s, entry->ctx.prev_prio);
-                SEQ_PUT_FIELD_RET(s, entry->ctx.prev_state);
-                SEQ_PUT_FIELD_RET(s, entry->ctx.next_pid);
-                SEQ_PUT_FIELD_RET(s, entry->ctx.next_prio);
-                SEQ_PUT_FIELD_RET(s, entry->ctx.next_state);
+                SEQ_PUT_FIELD_RET(s, field->ctx.prev_pid);
+                SEQ_PUT_FIELD_RET(s, field->ctx.prev_prio);
+                SEQ_PUT_FIELD_RET(s, field->ctx.prev_state);
+                SEQ_PUT_FIELD_RET(s, field->ctx.next_pid);
+                SEQ_PUT_FIELD_RET(s, field->ctx.next_prio);
+                SEQ_PUT_FIELD_RET(s, field->ctx.next_state);
                 break;
         case TRACE_SPECIAL:
         case TRACE_STACK:
-                SEQ_PUT_FIELD_RET(s, entry->special.arg1);
-                SEQ_PUT_FIELD_RET(s, entry->special.arg2);
-                SEQ_PUT_FIELD_RET(s, entry->special.arg3);
+                SEQ_PUT_FIELD_RET(s, field->special.arg1);
+                SEQ_PUT_FIELD_RET(s, field->special.arg2);
+                SEQ_PUT_FIELD_RET(s, field->special.arg3);
                 break;
         }
         return 1;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f69f86788c2b..6ddd6a6556cf 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -61,13 +61,12 @@ struct stack_entry {
 };
 
 /*
- * The trace entry - the most basic unit of tracing. This is what
+ * The trace field - the most basic unit of tracing. This is what
  * is printed in the end as a single line in the trace output, such as:
  *
  *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
  */
-struct trace_entry {
-        char                    type;
+struct trace_field {
         char                    cpu;
         char                    flags;
         char                    preempt_count;
@@ -83,6 +82,18 @@ struct trace_entry {
         };
 };
 
+struct trace_field_cont {
+        char                            buf[sizeof(struct trace_field)];
+};
+
+struct trace_entry {
+        char                            type;
+        union {
+                struct trace_field      field;
+                struct trace_field_cont cont;
+        };
+};
+
 #define TRACE_ENTRY_SIZE        sizeof(struct trace_entry)
 
 /*
diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index b13dc19dcbb4..9b7a936f4b1f 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -174,14 +174,14 @@ print_out:
 static int mmio_print_rw(struct trace_iterator *iter)
 {
         struct trace_entry *entry = iter->ent;
-        struct mmiotrace_rw *rw = &entry->mmiorw;
+        struct mmiotrace_rw *rw = &entry->field.mmiorw;
         struct trace_seq *s     = &iter->seq;
-        unsigned long long t    = ns2usecs(entry->t);
+        unsigned long long t    = ns2usecs(entry->field.t);
         unsigned long usec_rem  = do_div(t, 1000000ULL);
         unsigned secs           = (unsigned long)t;
         int ret = 1;
 
-        switch (entry->mmiorw.opcode) {
+        switch (entry->field.mmiorw.opcode) {
         case MMIO_READ:
                 ret = trace_seq_printf(s,
                         "R %d %lu.%06lu %d 0x%llx 0x%lx 0x%lx %d\n",
@@ -216,14 +216,14 @@ static int mmio_print_rw(struct trace_iterator *iter)
 static int mmio_print_map(struct trace_iterator *iter)
 {
         struct trace_entry *entry = iter->ent;
-        struct mmiotrace_map *m = &entry->mmiomap;
+        struct mmiotrace_map *m = &entry->field.mmiomap;
         struct trace_seq *s     = &iter->seq;
-        unsigned long long t    = ns2usecs(entry->t);
+        unsigned long long t    = ns2usecs(entry->field.t);
         unsigned long usec_rem  = do_div(t, 1000000ULL);
         unsigned secs           = (unsigned long)t;
         int ret = 1;
 
-        switch (entry->mmiorw.opcode) {
+        switch (entry->field.mmiorw.opcode) {
         case MMIO_PROBE:
                 ret = trace_seq_printf(s,
                         "MAP %lu.%06lu %d 0x%llx 0x%lx 0x%lx 0x%lx %d\n",