ratelimit: Use nolock_ret restructuring to collapse common case code

Now that unlock_ret releases the lock, then falls into nolock_ret, which
handles ->missed based on the value of ret, the common-case lock-held
code can be collapsed into a single "if" statement with a single-statement
"then" clause.

Yes, we could go further and just assign the "if" condition to ret,
but in the immortal words of MSDOS, "Are you sure?".

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Kuniyuki Iwashima <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: John Ogness <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>

Author: paulmckrcu

lib/ratelimit.c

@@ -88,17 +88,10 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 			}
 		}
 	}
-	if (burst) {
-		int n_left = atomic_read(&rs->rs_n_left);
 
-		/* The burst might have been taken by a parallel call. */
-
-		if (n_left > 0) {
-			n_left = atomic_dec_return(&rs->rs_n_left);
-			if (n_left >= 0)
-				ret = 1;
-		}
-	}
+	/* Note that the burst might be taken by a parallel call. */
+	if (burst && atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
+		ret = 1;
 
 unlock_ret:
 	raw_spin_unlock_irqrestore(&rs->lock, flags);