checkpatch: check for nested (un)?likely() calls

IS_ERR(), IS_ERR_OR_NULL(), IS_ERR_VALUE() and WARN*() already contain
unlikely() optimization internally.  Thus, there is no point in calling
these functions and defines under likely()/unlikely().

This check is based on the coccinelle rule developed by Enrico Weigelt
https://lore.kernel.org/lkml/1559767582-11081-1-git-send-email-info@metux.net/

Link: http://lkml.kernel.org/r/20190829165025.15750-1-efremov@linux.com
Signed-off-by: Denis Efremov <efremov@linux.com>
Cc: Joe Perches <joe@perches.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Anton Altaparmakov <anton@tuxera.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Boris Pismenny <borisp@mellanox.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Denis Efremov <efremov@linux.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Cc: Sean Paul <sean@poorly.run>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -6507,6 +6507,12 @@ sub process {
 			     "Using $1 should generally have parentheses around the comparison\n" . $herecurr);
 		}
 
+# nested likely/unlikely calls
+		if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) {
+			WARN("LIKELY_MISUSE",
+			     "nested (un)?likely() calls, $1 already uses unlikely() internally\n" . $herecurr);
+		}
+
 # whine mightly about in_atomic
 		if ($line =~ /\bin_atomic\s*\(/) {
 			if ($realfile =~ m@^drivers/@) {