powerpc/oprofile: reduce mmap_sem hold for exe_file

In the future mm->exe_file will be done without mmap_sem serialization,
thus isolate and reorganize the related code to make the transition
easier.  Good users will, make use of the more standard get_mm_exe_file(),
requiring only holding the mmap_sem to read the value, and relying on
reference counting to make sure that the exe file won't dissappear
underneath us while getting the dcookie.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Robert Richter <rric@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/arch/powerpc/oprofile/cell/spu_task_sync.c b/arch/powerpc/oprofile/cell/spu_task_sync.c
index 1c27831df1ac..ed7b0977072a 100644
--- a/arch/powerpc/oprofile/cell/spu_task_sync.c
+++ b/arch/powerpc/oprofile/cell/spu_task_sync.c
@@ -22,6 +22,7 @@
 #include <linux/kref.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
+#include <linux/file.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
 #include <linux/numa.h>
@@ -322,18 +323,20 @@ get_exec_dcookie_and_offset(struct spu *spu, unsigned int *offsetp,
         unsigned long app_cookie = 0;
         unsigned int my_offset = 0;
         struct vm_area_struct *vma;
+        struct file *exe_file;
         struct mm_struct *mm = spu->mm;
 
         if (!mm)
                 goto out;
 
-        down_read(&mm->mmap_sem);
-
-        if (mm->exe_file) {
-                app_cookie = fast_get_dcookie(&mm->exe_file->f_path);
-                pr_debug("got dcookie for %pD\n", mm->exe_file);
+        exe_file = get_mm_exe_file(mm);
+        if (exe_file) {
+                app_cookie = fast_get_dcookie(&exe_file->f_path);
+                pr_debug("got dcookie for %pD\n", exe_file);
+                fput(exe_file);
         }
 
+        down_read(&mm->mmap_sem);
         for (vma = mm->mmap; vma; vma = vma->vm_next) {
                 if (vma->vm_start > spu_ref || vma->vm_end <= spu_ref)
                         continue;