aio: remove no longer needed preempt_disable()

Based on feedback from Jens Axboe on 263782c1c9,
clean up get/put_reqs_available() to remove the no longer needed preempt_disable()
and preempt_enable() pair.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Jens Axboe <axboe@kernel.dk>

fs/aio.c

@@ -814,10 +814,8 @@ static void put_reqs_available(struct kioctx *ctx, unsigned nr)
 	struct kioctx_cpu *kcpu;
 	unsigned long flags;
 
-	preempt_disable();
-	kcpu = this_cpu_ptr(ctx->cpu);
-
 	local_irq_save(flags);
+	kcpu = this_cpu_ptr(ctx->cpu);
 	kcpu->reqs_available += nr;
 
 	while (kcpu->reqs_available >= ctx->req_batch * 2) {
@@ -826,7 +824,6 @@ static void put_reqs_available(struct kioctx *ctx, unsigned nr)
 	}
 
 	local_irq_restore(flags);
-	preempt_enable();
 }
 
 static bool get_reqs_available(struct kioctx *ctx)
@@ -835,10 +832,8 @@ static bool get_reqs_available(struct kioctx *ctx)
 	bool ret = false;
 	unsigned long flags;
 
-	preempt_disable();
-	kcpu = this_cpu_ptr(ctx->cpu);
-
 	local_irq_save(flags);
+	kcpu = this_cpu_ptr(ctx->cpu);
 	if (!kcpu->reqs_available) {
 		int old, avail = atomic_read(&ctx->reqs_available);
 
@@ -858,7 +853,6 @@ static bool get_reqs_available(struct kioctx *ctx)
 	kcpu->reqs_available--;
 out:
 	local_irq_restore(flags);
-	preempt_enable();
 	return ret;
 }