proc: don't do dummy rcu_read_lock/rcu_read_unlock on error path

rcu_read_lock()/rcu_read_unlock() is nop for TINY_RCU, but is not a nop
for, say, PREEMPT_RCU.

proc_fill_cache() is called without RCU lock, there is no need to
lock/unlock on error path, simply jump out of the loop.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -1928,21 +1928,22 @@ static int proc_readfd_common(struct file * filp, void * dirent,
 			     fd++, filp->f_pos++) {
 				char name[PROC_NUMBUF];
 				int len;
+				int rv;
 
 				if (!fcheck_files(files, fd))
 					continue;
 				rcu_read_unlock();
 
 				len = snprintf(name, sizeof(name), "%d", fd);
-				if (proc_fill_cache(filp, dirent, filldir,
-						    name, len, instantiate,
-						    p, &fd) < 0) {
-					rcu_read_lock();
-					break;
-				}
+				rv = proc_fill_cache(filp, dirent, filldir,
+						     name, len, instantiate, p,
+						     &fd);
+				if (rv < 0)
+					goto out_fd_loop;
 				rcu_read_lock();
 			}
 			rcu_read_unlock();
+out_fd_loop:
 			put_files_struct(files);
 	}
 out: