[PATCH 3/4] futex: use fast_gup()

[Peter Zijlstra]

Change the get_user_pages() call with fast_gup() which doesn't require holding
the mmap_sem thereby removing the mmap_sem from all fast paths.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/futex.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Index: linux-2.6/kernel/futex.c
===================================================================
--- linux-2.6.orig/kernel/futex.c
+++ linux-2.6/kernel/futex.c
@@ -232,9 +232,7 @@ static int get_futex_key(u32 __user *uad
 	}
 
 again:
-	down_read(&mm->mmap_sem);
-	err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
-	up_read(&mm->mmap_sem);
+	err = get_user_pages_fast(address, 1, 0, &page);
 	if (err < 0)
 		return err;
 


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