tracing: Clean up tracing_mark_write()

On gcc 4.5 the function tracing_mark_write() would give a warning
of page2 being uninitialized. This is due to a bug in gcc because
the logic prevents page2 from being used uninitialized, and
gcc 4.6+ does not complain (correctly).

Instead of adding a "unitialized" around page2, which could show
a bug later on, I combined page1 and page2 into an array map_pages[].
This binds the two and the two are modified according to nr_pages
(what gcc 4.5 seems to ignore). This no longer gives a warning with
gcc 4.5 nor with gcc 4.6.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 11 insertions, 13 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 48ef4960ec90..d1b3469b62e3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3875,14 +3875,14 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
         struct print_entry *entry;
         unsigned long irq_flags;
         struct page *pages[2];
+        void *map_page[2];
         int nr_pages = 1;
         ssize_t written;
-        void *page1;
-        void *page2;
         int offset;
         int size;
         int len;
         int ret;
+        int i;
 
         if (tracing_disabled)
                 return -EINVAL;
@@ -3921,9 +3921,8 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
                 goto out;
         }
 
-        page1 = kmap_atomic(pages[0]);
-        if (nr_pages == 2)
-                page2 = kmap_atomic(pages[1]);
+        for (i = 0; i < nr_pages; i++)
+                map_page[i] = kmap_atomic(pages[i]);
 
         local_save_flags(irq_flags);
         size = sizeof(*entry) + cnt + 2; /* possible \n added */
@@ -3941,10 +3940,10 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 
         if (nr_pages == 2) {
                 len = PAGE_SIZE - offset;
-                memcpy(&entry->buf, page1 + offset, len);
-                memcpy(&entry->buf[len], page2, cnt - len);
+                memcpy(&entry->buf, map_page[0] + offset, len);
+                memcpy(&entry->buf[len], map_page[1], cnt - len);
         } else
-                memcpy(&entry->buf, page1 + offset, cnt);
+                memcpy(&entry->buf, map_page[0] + offset, cnt);
 
         if (entry->buf[cnt - 1] != '\n') {
                 entry->buf[cnt] = '\n';
@@ -3959,11 +3958,10 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
         *fpos += written;
 
  out_unlock:
-        if (nr_pages == 2)
-                kunmap_atomic(page2);
-        kunmap_atomic(page1);
-        while (nr_pages > 0)
-                put_page(pages[--nr_pages]);
+        for (i = 0; i < nr_pages; i++){
+                kunmap_atomic(map_page[i]);
+                put_page(pages[i]);
+        }
  out:
         return written;
 }