futex: get_futex_key, get_key_refs and drop_key_refs

lguest uses the convenient futex infrastructure for inter-domain I/O, so
expose get_futex_key, get_key_refs (renamed get_futex_key_refs) and
drop_key_refs (renamed drop_futex_key_refs).  Also means we need to expose the
union that these use.

No code changes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 43 insertions, 36 deletions

diff --git a/include/linux/futex.h b/include/linux/futex.h
index 3f153b4e156c..820125c628c1 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -100,6 +100,35 @@ long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
 extern int
 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 
+/*
+ * Futexes are matched on equal values of this key.
+ * The key type depends on whether it's a shared or private mapping.
+ * Don't rearrange members without looking at hash_futex().
+ *
+ * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
+ * We set bit 0 to indicate if it's an inode-based key.
+ */
+union futex_key {
+        struct {
+                unsigned long pgoff;
+                struct inode *inode;
+                int offset;
+        } shared;
+        struct {
+                unsigned long address;
+                struct mm_struct *mm;
+                int offset;
+        } private;
+        struct {
+                unsigned long word;
+                void *ptr;
+                int offset;
+        } both;
+};
+int get_futex_key(u32 __user *uaddr, union futex_key *key);
+void get_futex_key_refs(union futex_key *key);
+void drop_futex_key_refs(union futex_key *key);
+
 #ifdef CONFIG_FUTEX
 extern void exit_robust_list(struct task_struct *curr);
 extern void exit_pi_state_list(struct task_struct *curr);
diff --git a/kernel/futex.c b/kernel/futex.c
index 5a270b5e3f95..7ae2f50641ed 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -48,6 +48,7 @@
 #include <linux/pagemap.h>
 #include <linux/syscalls.h>
 #include <linux/signal.h>
+#include <linux/module.h>
 #include <asm/futex.h>
 
 #include "rtmutex_common.h"
@@ -55,32 +56,6 @@
 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
 
 /*
- * Futexes are matched on equal values of this key.
- * The key type depends on whether it's a shared or private mapping.
- * Don't rearrange members without looking at hash_futex().
- *
- * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
- * We set bit 0 to indicate if it's an inode-based key.
- */
-union futex_key {
-        struct {
-                unsigned long pgoff;
-                struct inode *inode;
-                int offset;
-        } shared;
-        struct {
-                unsigned long address;
-                struct mm_struct *mm;
-                int offset;
-        } private;
-        struct {
-                unsigned long word;
-                void *ptr;
-                int offset;
-        } both;
-};
-
-/*
  * Priority Inheritance state:
  */
 struct futex_pi_state {
@@ -175,7 +150,7 @@ static inline int match_futex(union futex_key *key1, union futex_key *key2)
  *
  * Should be called with &current->mm->mmap_sem but NOT any spinlocks.
  */
-static int get_futex_key(u32 __user *uaddr, union futex_key *key)
+int get_futex_key(u32 __user *uaddr, union futex_key *key)
 {
         unsigned long address = (unsigned long)uaddr;
         struct mm_struct *mm = current->mm;
@@ -246,6 +221,7 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key)
         }
         return err;
 }
+EXPORT_SYMBOL_GPL(get_futex_key);
 
 /*
  * Take a reference to the resource addressed by a key.
@@ -254,7 +230,7 @@ static int get_futex_key(u32 __user *uaddr, union futex_key *key)
  * NOTE: mmap_sem MUST be held between get_futex_key() and calling this
  * function, if it is called at all.  mmap_sem keeps key->shared.inode valid.
  */
-static inline void get_key_refs(union futex_key *key)
+inline void get_futex_key_refs(union futex_key *key)
 {
         if (key->both.ptr != 0) {
                 if (key->both.offset & 1)
@@ -263,12 +239,13 @@ static inline void get_key_refs(union futex_key *key)
                         atomic_inc(&key->private.mm->mm_count);
         }
 }
+EXPORT_SYMBOL_GPL(get_futex_key_refs);
 
 /*
  * Drop a reference to the resource addressed by a key.
  * The hash bucket spinlock must not be held.
  */
-static void drop_key_refs(union futex_key *key)
+void drop_futex_key_refs(union futex_key *key)
 {
         if (key->both.ptr != 0) {
                 if (key->both.offset & 1)
@@ -277,6 +254,7 @@ static void drop_key_refs(union futex_key *key)
                         mmdrop(key->private.mm);
         }
 }
+EXPORT_SYMBOL_GPL(drop_futex_key_refs);
 
 static inline int get_futex_value_locked(u32 *dest, u32 __user *from)
 {
@@ -873,7 +851,7 @@ static int futex_requeue(u32 __user *uaddr1, u32 __user *uaddr2,
                                 this->lock_ptr = &hb2->lock;
                         }
                         this->key = key2;
-                        get_key_refs(&key2);
+                        get_futex_key_refs(&key2);
                         drop_count++;
 
                         if (ret - nr_wake >= nr_requeue)
@@ -886,9 +864,9 @@ out_unlock:
         if (hb1 != hb2)
                 spin_unlock(&hb2->lock);
 
-        /* drop_key_refs() must be called outside the spinlocks. */
+        /* drop_futex_key_refs() must be called outside the spinlocks. */
         while (--drop_count >= 0)
-                drop_key_refs(&key1);
+                drop_futex_key_refs(&key1);
 
 out:
         up_read(&current->mm->mmap_sem);
@@ -906,7 +884,7 @@ queue_lock(struct futex_q *q, int fd, struct file *filp)
 
         init_waitqueue_head(&q->waiters);
 
-        get_key_refs(&q->key);
+        get_futex_key_refs(&q->key);
         hb = hash_futex(&q->key);
         q->lock_ptr = &hb->lock;
 
@@ -925,7 +903,7 @@ static inline void
 queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
 {
         spin_unlock(&hb->lock);
-        drop_key_refs(&q->key);
+        drop_futex_key_refs(&q->key);
 }
 
 /*
@@ -980,7 +958,7 @@ static int unqueue_me(struct futex_q *q)
                 ret = 1;
         }
 
-        drop_key_refs(&q->key);
+        drop_futex_key_refs(&q->key);
         return ret;
 }
 
@@ -999,7 +977,7 @@ static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb)
 
         spin_unlock(&hb->lock);
 
-        drop_key_refs(&q->key);
+        drop_futex_key_refs(&q->key);
 }
 
 static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)