futex: Remove redundant pagefault_disable in futex_atomic_cmpxchg_inatomic()

kernel/futex.c disables page faults before calling
futex_atomic_cmpxchg_inatomic(), so there is no need to do it again
within that function.
    
Signed-off-by: Michel Lespinasse <[email protected]>
Cc: Darren Hart <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Russell King <[email protected]>
Cc: David Howells <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Linus Torvalds <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>

Author: walken-google

arch/arm/include/asm/futex.h

@@ -95,7 +95,8 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
 		return -EFAULT;
 
-	pagefault_disable();	/* implies preempt_disable() */
+	/* Note that preemption is disabled by futex_atomic_cmpxchg_inatomic
+	 * call sites. */
 
 	__asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
 	"1:	" T(ldr) "	%0, [%3]\n"
@@ -115,8 +116,6 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 	: "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
 	: "cc", "memory");
 
-	pagefault_enable();	/* subsumes preempt_enable() */
-
 	return val;
 }