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@perches.com>
Reported-by: Theodore Ts'o <tytso@mit.edu>
Original-patch-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index b351805149a5461789cafb350ecc83d5ff03f127..3661ffc7af2378912d362449bd4166c970c92c36 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/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;
 
                                }