perf: Factor out strncpy() in perf_event_mmap_event()

While this is really minor, but strncpy() does the unnecessary
zero-padding till the end of tmp[16] and it is called every time
we are going to use the string literal.

Turn these strncpy()'s into the single strlcpy() under the new
label, saves 72 bytes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131017182417.GA17753@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 17b3c6c..4dc078d 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5144,8 +5144,8 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
 
                buf = kmalloc(PATH_MAX, GFP_KERNEL);
                if (!buf) {
-                       name = strncpy(tmp, "//enomem", sizeof(tmp));
-                       goto got_name;
+                       name = "//enomem";
+                       goto cpy_name;
                }
                /*
                 * d_path() works from the end of the rb backwards, so we
@@ -5154,8 +5154,8 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
                 */
                name = d_path(&file->f_path, buf, PATH_MAX - sizeof(u64));
                if (IS_ERR(name)) {
-                       name = strncpy(tmp, "//toolong", sizeof(tmp));
-                       goto got_name;
+                       name = "//toolong";
+                       goto cpy_name;
                }
                inode = file_inode(vma->vm_file);
                dev = inode->i_sb->s_dev;
@@ -5163,30 +5163,30 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
                gen = inode->i_generation;
                maj = MAJOR(dev);
                min = MINOR(dev);
-
+               goto got_name;
        } else {
                name = (char *)arch_vma_name(vma);
-               if (name) {
-                       name = strncpy(tmp, name, sizeof(tmp) - 1);
-                       tmp[sizeof(tmp) - 1] = '\0';
-                       goto got_name;
-               }
+               if (name)
+                       goto cpy_name;
 
                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;
+                       name = "[heap]";
+                       goto cpy_name;
                }
                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;
+                       name = "[stack]";
+                       goto cpy_name;
                }
 
-               name = strncpy(tmp, "//anon", sizeof(tmp));
-               goto got_name;
+               name = "//anon";
+               goto cpy_name;
        }
 
+cpy_name:
+       strlcpy(tmp, name, sizeof(tmp));
+       name = tmp;
 got_name:
        /*
         * Since our buffer works in 8 byte units we need to align our string