linux-kernel - Re: [PATCH] IB/mlx5: Fix a parameter of find_first

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Date:   Fri, 26 Aug 2016 09:52:40 +0000
From:   Majd Dibbiny <majd@...lanox.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
CC:     Matan Barak <matanb@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "sean.hefty@...el.com" <sean.hefty@...el.com>,
        "hal.rosenstock@...il.com" <hal.rosenstock@...il.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH] IB/mlx5: Fix a parameter of find_first_bit

Acked-by: Majd Dibbiny <majd@...lanox.com>

> On Aug 26, 2016, at 8:25 AM, Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
> 
> The 2nd parameter of 'find_first_bit' is the number of bits to search.
> In this case, we are passing 'sizeof(tmp)' which is likely to be 4 or 8
> because 'tmp' is an 'unsigned long'.
> 
> It is likely that the number of bits of 'tmp' was expected here. So use
> BITS_PER_LONG instead.
> 
> It has been spotted by the following coccinelle script:
> @@
> expression ret, x;
> 
> @@
> *  ret = \(find_first_bit \| find_first_zero_bit\) (x, sizeof(...));
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> __ffs could be used to reduce code verbosity
> ---
> drivers/infiniband/hw/mlx5/mem.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/mem.c b/drivers/infiniband/hw/mlx5/mem.c
> index 40df2cca0609..996b54e366b0 100644
> --- a/drivers/infiniband/hw/mlx5/mem.c
> +++ b/drivers/infiniband/hw/mlx5/mem.c
> @@ -71,7 +71,7 @@ void mlx5_ib_cont_pages(struct ib_umem *umem, u64 addr, int *count, int *shift,
> 
>    addr = addr >> page_shift;
>    tmp = (unsigned long)addr;
> -    m = find_first_bit(&tmp, sizeof(tmp));
> +    m = find_first_bit(&tmp, BITS_PER_LONG);
>    skip = 1 << m;
>    mask = skip - 1;
>    i = 0;
> @@ -81,7 +81,7 @@ void mlx5_ib_cont_pages(struct ib_umem *umem, u64 addr, int *count, int *shift,
>        for (k = 0; k < len; k++) {
>            if (!(i & mask)) {
>                tmp = (unsigned long)pfn;
> -                m = min_t(unsigned long, m, find_first_bit(&tmp, sizeof(tmp)));
> +                m = min_t(unsigned long, m, find_first_bit(&tmp, BITS_PER_LONG));
>                skip = 1 << m;
>                mask = skip - 1;
>                base = pfn;
> @@ -89,7 +89,7 @@ void mlx5_ib_cont_pages(struct ib_umem *umem, u64 addr, int *count, int *shift,
>            } else {
>                if (base + p != pfn) {
>                    tmp = (unsigned long)p;
> -                    m = find_first_bit(&tmp, sizeof(tmp));
> +                    m = find_first_bit(&tmp, BITS_PER_LONG);
>                    skip = 1 << m;
>                    mask = skip - 1;
>                    base = pfn;
> -- 
> 2.7.4
> 
> 
> ---
> L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast.
> https://www.avast.com/antivirus
> 
> --
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