linux-kernel - [PATCH] checkpatch: Emit fewer kmalloc

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Date:	Tue, 01 Jul 2014 14:33:07 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Fabian Frederick <fabf@...net.be>, Theodore Ts'o <tytso@....edu>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] 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: Joe Perches <joe@...ches.com>
Noticed-by: Theodore Ts'o <tytso@....edu>
Original-patch-by: Fabian Frederick <fabf@...net.be>
---
 scripts/checkpatch.pl | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 6c7cbaf..e0d0ead 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4486,22 +4486,23 @@ 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;
 
 				}



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