mm: add new mmgrab() helper

Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:

  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
  git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'

This is needed for a later patch that hooks into the helper, but might
be a worthwhile cleanup on its own.

(Michal Hocko provided most of the kerneldoc comment.)

Link: http://lkml.kernel.org/r/20161218123229.22952-1-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 6 insertions, 6 deletions

diff --git a/arch/sparc/kernel/leon_smp.c b/arch/sparc/kernel/leon_smp.c
index 71e16f2241c2..b99d33797e1d 100644
--- a/arch/sparc/kernel/leon_smp.c
+++ b/arch/sparc/kernel/leon_smp.c
@@ -93,7 +93,7 @@ void leon_cpu_pre_online(void *arg)
                              : "memory" /* paranoid */);
 
         /* Attach to the address space of init_task. */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 
         while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index 90a02cb64e20..8e3e13924594 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -122,7 +122,7 @@ void smp_callin(void)
         current_thread_info()->new_child = 0;
 
         /* Attach to the address space of init_task. */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 
         /* inform the notifiers about the new cpu */
diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
index 9d98e5002a09..7b55c50eabe5 100644
--- a/arch/sparc/kernel/sun4d_smp.c
+++ b/arch/sparc/kernel/sun4d_smp.c
@@ -93,7 +93,7 @@ void sun4d_cpu_pre_online(void *arg)
         show_leds(cpuid);
 
         /* Attach to the address space of init_task. */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 
         local_ops->cache_all();
diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
index 278c40abce82..633c4cf6fdb0 100644
--- a/arch/sparc/kernel/sun4m_smp.c
+++ b/arch/sparc/kernel/sun4m_smp.c
@@ -59,7 +59,7 @@ void sun4m_cpu_pre_online(void *arg)
                              : "memory" /* paranoid */);
 
         /* Attach to the address space of init_task. */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 
         while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
diff --git a/arch/sparc/kernel/traps_32.c b/arch/sparc/kernel/traps_32.c
index 4f21df7d4f13..ecddac5a4c96 100644
--- a/arch/sparc/kernel/traps_32.c
+++ b/arch/sparc/kernel/traps_32.c
@@ -448,7 +448,7 @@ void trap_init(void)
                 thread_info_offsets_are_bolixed_pete();
 
         /* Attach to the address space of init_task. */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 
         /* NOTE: Other cpus have this done as they are started
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index dfc97a47c9a0..e022d7b00390 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2837,6 +2837,6 @@ void __init trap_init(void)
         /* Attach to the address space of init_task.  On SMP we
          * do this in smp.c:smp_callin for other cpus.
          */
-        atomic_inc(&init_mm.mm_count);
+        mmgrab(&init_mm);
         current->active_mm = &init_mm;
 }