perf: Kill the dead !vma->vm_mm code in perf_event_mmap_event()

1. perf_event_mmap(vma) is never called with a gate_vma-like arg,
   remove the "if (!vma->vm_mm)" code.

2. arch_vma_name() can use the chached value of mmap_event->vma.

3. Change the code to not call arch_vma_name() twice.

4. Purely cosmetic, but since we use "goto got_name" all the time
   remove "else" from "[stack]" branch just for symmetry.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131016200945.GB23214@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 028dad97760d..3ea560551a2a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5136,21 +5136,19 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
                 min = MINOR(dev);
 
         } else {
-                if (arch_vma_name(mmap_event->vma)) {
-                        name = strncpy(tmp, arch_vma_name(mmap_event->vma),
-                                       sizeof(tmp) - 1);
+                name = arch_vma_name(vma);
+                if (name) {
+                        name = strncpy(tmp, name, sizeof(tmp) - 1);
                         tmp[sizeof(tmp) - 1] = '\0';
                         goto got_name;
                 }
 
-                if (!vma->vm_mm) {
-                        name = strncpy(tmp, "[vdso]", sizeof(tmp));
-                        goto got_name;
-                } else if (vma->vm_start <= vma->vm_mm->start_brk &&
+                if (vma->vm_start <= vma->vm_mm->start_brk &&
                                 vma->vm_end >= vma->vm_mm->brk) {
                         name = strncpy(tmp, "[heap]", sizeof(tmp));
                         goto got_name;
-                } else if (vma->vm_start <= vma->vm_mm->start_stack &&
+                }
+                if (vma->vm_start <= vma->vm_mm->start_stack &&
                                 vma->vm_end >= vma->vm_mm->start_stack) {
                         name = strncpy(tmp, "[stack]", sizeof(tmp));
                         goto got_name;