[PATCH] Futex bugfixes.

This uses page_cache_release() instead of put_page(), as it might
be a pagecache page.

diff --git a/kernel/futex.c b/kernel/futex.c
index bdff307969efacdfa63cc7c7eaf166fcd9ddf78e..332acaa2d6c56c78a1641759ddd4a8df5d96c1cd 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -70,6 +70,14 @@ static inline void tell_waiter(struct futex_q *q)
        wake_up_all(&q->waiters);
 }
 
+static inline void unpin_page(struct page *page)
+{
+       /* Avoid releasing the page which is on the LRU list.  I don't
+           know if this is correct, but it stops the BUG() in
+           __free_pages_ok(). */
+       page_cache_release(page);
+}
+
 static int futex_wake(struct list_head *head,
                      struct page *page,
                      unsigned int offset,
@@ -130,9 +138,9 @@ static struct page *pin_page(unsigned long page_start)
        int err;
 
        down_read(&mm->mmap_sem);
-       err = get_user_pages(current, current->mm, page_start,
+       err = get_user_pages(current, mm, page_start,
                             1 /* one page */,
-                            1 /* writable */,
+                            0 /* writable not important */,
                             0 /* don't force */,
                             &page,
                             NULL /* don't return vmas */);
@@ -223,7 +231,7 @@ asmlinkage int sys_futex(void *uaddr, int op, int val, struct timespec *utime)
        default:
                ret = -EINVAL;
        }
-       page_cache_release(page);
+       unpin_page(page);
 
        return ret;
 }