From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri, 26 Sep 2008 17:32:22 +0000 (+0200)
Subject: futex: use fast_gup()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=734b05b10e51d4ba38c8fc3ee02e846aab09eedf;p=linux-beck.git

futex: use fast_gup()

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@chello.nl>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/futex.c b/kernel/futex.c
index 6a726684217e..facf17d1a705 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -232,9 +232,7 @@ static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared,
 	}
 
 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;