Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  VFS: Fix race between CPU hotplug and lglocks

1 files changed, 32 insertions, 4 deletions

diff --git a/include/linux/lglock.h b/include/linux/lglock.h
index f549056fb20b..87f402ccec55 100644
--- a/include/linux/lglock.h
+++ b/include/linux/lglock.h
@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/lockdep.h>
 #include <linux/percpu.h>
+#include <linux/cpu.h>
 
 /* can make br locks by using local lock for read side, global lock for write */
 #define br_lock_init(name)      name##_lock_init()
@@ -72,9 +73,31 @@
 
 #define DEFINE_LGLOCK(name)                                             \
                                                                         \
+ DEFINE_SPINLOCK(name##_cpu_lock);                                      \
+ cpumask_t name##_cpus __read_mostly;                                   \
  DEFINE_PER_CPU(arch_spinlock_t, name##_lock);                          \
  DEFINE_LGLOCK_LOCKDEP(name);                                           \
                                                                         \
+ static int                                                             \
+ name##_lg_cpu_callback(struct notifier_block *nb,                      \
+                                unsigned long action, void *hcpu)       \
+ {                                                                      \
+        switch (action & ~CPU_TASKS_FROZEN) {                           \
+        case CPU_UP_PREPARE:                                            \
+                spin_lock(&name##_cpu_lock);                            \
+                cpu_set((unsigned long)hcpu, name##_cpus);              \
+                spin_unlock(&name##_cpu_lock);                          \
+                break;                                                  \
+        case CPU_UP_CANCELED: case CPU_DEAD:                            \
+                spin_lock(&name##_cpu_lock);                            \
+                cpu_clear((unsigned long)hcpu, name##_cpus);            \
+                spin_unlock(&name##_cpu_lock);                          \
+        }                                                               \
+        return NOTIFY_OK;                                               \
+ }                                                                      \
+ static struct notifier_block name##_lg_cpu_notifier = {                \
+        .notifier_call = name##_lg_cpu_callback,                        \
+ };                                                                     \
  void name##_lock_init(void) {                                          \
         int i;                                                          \
         LOCKDEP_INIT_MAP(&name##_lock_dep_map, #name, &name##_lock_key, 0); \
@@ -83,6 +106,11 @@
                 lock = &per_cpu(name##_lock, i);                        \
                 *lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;     \
         }                                                               \
+        register_hotcpu_notifier(&name##_lg_cpu_notifier);              \
+        get_online_cpus();                                              \
+        for_each_online_cpu(i)                                          \
+                cpu_set(i, name##_cpus);                                \
+        put_online_cpus();                                              \
  }                                                                      \
  EXPORT_SYMBOL(name##_lock_init);                                       \
                                                                         \
@@ -124,9 +152,9 @@
                                                                         \
  void name##_global_lock_online(void) {                                 \
         int i;                                                          \
-        preempt_disable();                                              \
+        spin_lock(&name##_cpu_lock);                                    \
         rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_);           \
-        for_each_online_cpu(i) {                                        \
+        for_each_cpu(i, &name##_cpus) {                                 \
                 arch_spinlock_t *lock;                                  \
                 lock = &per_cpu(name##_lock, i);                        \
                 arch_spin_lock(lock);                                   \
@@ -137,12 +165,12 @@
  void name##_global_unlock_online(void) {                               \
         int i;                                                          \
         rwlock_release(&name##_lock_dep_map, 1, _RET_IP_);              \
-        for_each_online_cpu(i) {                                        \
+        for_each_cpu(i, &name##_cpus) {                                 \
                 arch_spinlock_t *lock;                                  \
                 lock = &per_cpu(name##_lock, i);                        \
                 arch_spin_unlock(lock);                                 \
         }                                                               \
-        preempt_enable();                                               \
+        spin_unlock(&name##_cpu_lock);                                  \
  }                                                                      \
  EXPORT_SYMBOL(name##_global_unlock_online);                            \
                                                                         \