linux-kernel - Re: [PATCH 01/10] dm snapshot: Use kmalloc_array() in init_origin

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Date:   Thu, 29 Sep 2016 03:02:56 -0700
From:   Joe Perches <joe@...ches.com>
To:     Paul Bolle <pebolle@...cali.nl>, Andy Whitcroft <apw@...onical.com>
Cc:     SF Markus Elfring <elfring@...rs.sourceforge.net>,
        dm-devel@...hat.com, linux-raid@...r.kernel.org,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Shaohua Li <shli@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH 01/10] dm snapshot: Use kmalloc_array() in
 init_origin_hash()

On Thu, 2016-09-29 at 11:54 +0200, Paul Bolle wrote:
> Andy, Joe,
> 
> On Thu, 2016-09-29 at 11:07 +0200, SF Markus Elfring wrote:
> > * Multiplications for the size determination of memory allocations
> >   indicated that array data structures should be processed.
> >   Thus use the corresponding function "kmalloc_array".
> > 
> >   This issue was detected by using the Coccinelle software.
> 
> 
> We have no hope of fixing Markus' homegrown coccinelle script. But we
> could try to fix the checkpatch false positive here.

What's the false positive?

I get:

$ ./scripts/checkpatch.pl -f drivers/md/dm-snap.c --show-types --types=alloc_with_multiply
WARNING:ALLOC_WITH_MULTIPLY: Prefer kmalloc_array over kmalloc with multiply
#329: FILE: drivers/md/dm-snap.c:329:
+	_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),

WARNING:ALLOC_WITH_MULTIPLY: Prefer kmalloc_array over kmalloc with multiply
#338: FILE: drivers/md/dm-snap.c:338:
+	_dm_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),

total: 0 errors, 2 warnings, 2490 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

drivers/md/dm-snap.c has style problems, please review.

NOTE: Used message types: ALLOC_WITH_MULTIPLY

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.