checkpatch: emit fewer kmalloc_array/kcalloc conversion warnings

Avoid matching allocs that appear to be known small multiplications of a
sizeof with a constant because gcc as of 4.8 cannot optimize the code in
a calloc() exactly the same way as an alloc().

Look for numeric constants or what appear to be upper case only macro
#defines.
Signed-off-by: NJoe Perches <joe@perches.com>
Reported-by: NTheodore Ts'o <tytso@mit.edu>
Original-patch-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -4487,22 +4487,23 @@ sub process {
 
 # check for k[mz]alloc with multiplies that could be kmalloc_array/kcalloc
 		if ($^V && $^V ge 5.10.0 &&
-		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*(k[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/) {
+		    $line =~ /\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*(k[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)\s*,/) {
 			my $oldfunc = $3;
 			my $a1 = $4;
 			my $a2 = $10;
 			my $newfunc = "kmalloc_array";
 			$newfunc = "kcalloc" if ($oldfunc eq "kzalloc");
-			if ($a1 =~ /^sizeof\s*\S/ || $a2 =~ /^sizeof\s*\S/) {
+			my $r1 = $a1;
+			my $r2 = $a2;
+			if ($a1 =~ /^sizeof\s*\S/) {
+				$r1 = $a2;
+				$r2 = $a1;
+			}
+			if ($r1 !~ /^sizeof\b/ && $r2 =~ /^sizeof\s*\S/ &&
+			    !($r1 =~ /^$Constant$/ || $r1 =~ /^[A-Z_][A-Z0-9_]*$/)) {
 				if (WARN("ALLOC_WITH_MULTIPLY",
 					 "Prefer $newfunc over $oldfunc with multiply\n" . $herecurr) &&
 				    $fix) {
-					my $r1 = $a1;
-					my $r2 = $a2;
-					if ($a1 =~ /^sizeof\s*\S/) {
-						$r1 = $a2;
-						$r2 = $a1;
-					}
 					$fixed[$linenr - 1] =~ s/\b($Lval)\s*\=\s*(?:$balanced_parens)?\s*(k[mz]alloc)\s*\(\s*($FuncArg)\s*\*\s*($FuncArg)/$1 . ' = ' . "$newfunc(" . trim($r1) . ', ' . trim($r2)/e;
 
 				}