Re: [PATCH 2/3] md/bitmap: Delete an unnecessary check before the function call "kfree"

NeilBrown
2015-02-02T19:46:03Z

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On Mon, 02 Feb 2015 16:20:42 +0100 SF Markus Elfring
<elfring@users.sourceforge.net> wrote:

> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Mon, 2 Feb 2015 15:10:57 +0100
>
> The kfree() function tests whether its argument is NULL and then
> returns immediately. Thus the test around the call is not needed.
>
> * This issue was detected by using the Coccinelle software.
>
> * Let us also move an assignment for the variable "pages" to the place
> directly before it is really needed for a loop.
>
> * Let us also move another kfree() call into a block which should belong
> to a previous check for the variable "bp".
>
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> drivers/md/bitmap.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
> index da3604e..47d72df 100644
> --- a/drivers/md/bitmap.c
> +++ b/drivers/md/bitmap.c
> @@ -1586,15 +1586,15 @@ static void bitmap_free(struct bitmap *bitmap)
> bitmap_file_unmap(&bitmap->storage);
>
> bp = bitmap->counts.bp;
> - pages = bitmap->counts.pages;
>
> /* free all allocated memory */
> -
> - if (bp) /* deallocate the page memory */
> + if (bp) { /* deallocate the page memory */
> + pages = bitmap->counts.pages;
> for (k = 0; k < pages; k++)
> - if (bp[k].map && !bp[k].hijacked)
> + if (!bp[k].hijacked)
> kfree(bp[k].map);
> - kfree(bp);
> + kfree(bp);
> + }
> kfree(bitmap);
> }
>

Hi,
I'm somewhat amused that you removed a test for one kfree, but imposed a
test on another. I realised the second test was already there, but why not
just:

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index da3604e73e8a..ad13b2e1bf1f 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1592,7 +1592,7 @@ static void bitmap_free(struct bitmap *bitmap)

if (bp) /* deallocate the page memory */
for (k = 0; k < pages; k++)
- if (bp[k].map && !bp[k].hijacked)
+ if (!bp[k].hijacked)
kfree(bp[k].map);
kfree(bp);
kfree(bitmap);

It makes the intention of the patch much clearer.

I'd probably prefer to leave the code as it is. I don't think either patch
is really an improvement in readability, and readability trumps performance
in places like this.

Thanks,
NeilBrown

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