linux-kernel - Re: [PATCH v2 5/5] lib: scatterlist: move SG pool code from SCSI driver to lib/sg

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Date:	Mon, 4 Apr 2016 13:15:45 -0700
From:	Ming Lin <mlin@...nel.org>
To:	kbuild test robot <lkp@...el.com>
Cc:	Ming Lin <mlin@...nel.org>, kbuild-all@...org,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 5/5] lib: scatterlist: move SG pool code from SCSI
 driver to lib/sg_pool.c

On Tue, Mar 22, 2016 at 7:38 PM, kbuild test robot <lkp@...el.com> wrote:
> Hi Ming,
>
> [auto build test WARNING on scsi/for-next]
> [also build test WARNING on v4.5 next-20160322]
> [if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
>
> url:    https://github.com/0day-ci/linux/commits/Ming-Lin/mempool-based-chained-scatterlist-alloc-free-api/20160323-060710
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi.git for-next
>
>
> coccinelle warnings: (new ones prefixed by >>)
>
>>> lib/sg_pool.c:152:3-18: WARNING: NULL check before freeing functions like kfree, debugfs_remove, debugfs_remove_recursive or usb_free_urb is not needed. Maybe consider reorganizing relevant code to avoid passing NULL values.
>    lib/sg_pool.c:154:3-21: WARNING: NULL check before freeing functions like kfree, debugfs_remove, debugfs_remove_recursive or usb_free_urb is not needed. Maybe consider reorganizing relevant code to avoid passing NULL values.

mempool_destroy()/kmem_cache_destroy() is OK to accept NULL pointer.
But the logic is more readable that we do NULL check when cleanup due to error.

cleanup_sdb:
        for (i = 0; i < SG_MEMPOOL_NR; i++) {
                struct sg_pool *sgp = sg_pools + i;
                if (sgp->pool)
                        mempool_destroy(sgp->pool);
                if (sgp->slab)
                        kmem_cache_destroy(sgp->slab);
        }

I'll keep the NULL check if no objection.

Thanks.