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SubjectRe: [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
Julia Lawall wrote:
> From: Julia Lawall <julia@diku.dk>
>
> If the NULL test is necessary, then the dereference should be moved below
> the NULL test.
>
> The semantic patch that makes this change is as follows:
> (http://www.emn.fr/x-info/coccinelle/)
>
> // <smpl>
> @@
> type T;
> expression E,E1;
> identifier i,fld;
> statement S;
> @@
>
> - T i = E->fld;
> + T i;
> ... when != E=E1
> when != i
> BUG_ON (E == NULL||
> - i
> + E->fld
> == NULL || ...);
> + i = E->fld;
> // </smpl>
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> drivers/mmc/host/omap.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
> index e7a331d..89281ab 100644
> --- a/drivers/mmc/host/omap.c
> +++ b/drivers/mmc/host/omap.c
> @@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct work_struct *work)
>
> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
> {
> - struct mmc_omap_host *host = slot->host;
> + struct mmc_omap_host *host;
> unsigned long flags;
> int i;
>
> - BUG_ON(slot == NULL || host->mmc == NULL);
> + BUG_ON(slot == NULL || slot->host->mmc == NULL);
> + host = slot->host;
>
> if (clk_enabled)
> /* Keeps clock running for at least 8 cycles on valid freq */
> --

If slot is NULL it will oops anyway, so the following is better IMHO:

static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
{
struct mmc_omap_host *host = slot->host;
unsigned long flags;
int i;

> - BUG_ON(slot == NULL || host->mmc == NULL);
> + BUG_ON(host->mmc == NULL);

if (clk_enabled)
/* Keeps clock running for at least 8 cycles on valid freq */


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