sysctl: Reduce dput(child) calls in proc_sys_fill_cache()

Replace two dput(child) calls with one that occurs immediately before
the IS_ERR evaluation. This transformation can be performed because
dput() gets called regardless of the value returned by IS_ERR(res).

This issue was transformed by using a script for the
semantic patch language like the following.
<SmPL>
@extended_adjustment@
expression e, f != { mutex_unlock }, x, y;
@@
+f(e);
 if (...)
 {
 <+... when != \( e = x \| y(..., &e, ...) \)
-   f(e);
 ...+>
 }
-f(e);
</SmPL>

Signed-off-by: Markus Elfring <[email protected]>
Reviewed-by: Joel Granados <[email protected]>
Signed-off-by: Joel Granados <[email protected]>

Author: elfring

fs/proc/proc_sysctl.c

@@ -704,11 +704,11 @@ static bool proc_sys_fill_cache(struct file *file,
 			res = d_splice_alias(inode, child);
 			d_lookup_done(child);
 			if (unlikely(res)) {
-				if (IS_ERR(res)) {
-					dput(child);
-					return false;
-				}
 				dput(child);
+
+				if (IS_ERR(res))
+					return false;
+
 				child = res;
 			}
 		}