Messages in this thread | | | Date | Mon, 9 Nov 2015 16:14:50 +0200 | Subject | Re: [PATCH V2 2/3] scsi: fix compiler warning for sg | From | Andy Shevchenko <> |
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On Mon, Nov 9, 2015 at 3:57 AM, Sinan Kaya <okaya@codeaurora.org> wrote: > The MULDIV macro has been designed for small numbers. > Compiler emits an overflow warning on 64 bit systems. > This patch uses 64 bit numbers in order to suppress > warning. > > Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
> --- > drivers/scsi/sg.c | 20 +++++++++++++------- > 1 file changed, 13 insertions(+), 7 deletions(-) > > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index 9d7b7db..112d8974 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -51,6 +51,7 @@ static int sg_version_num = 30536; /* 2 digits for each component */ > #include <linux/atomic.h> > #include <linux/ratelimit.h> > #include <linux/uio.h> > +#include <asm/div64.h> > > #include "scsi.h" > #include <scsi/scsi_dbg.h> > @@ -85,12 +86,17 @@ static void sg_proc_cleanup(void); > * Replacing muldiv(x) by muldiv(x)=((x % d) * m) / d + int(x / d) * m > * calculates the same, but prevents the overflow when both m and d > * are "small" numbers (like HZ and USER_HZ). > - * Of course an overflow is inavoidable if the result of muldiv doesn't fit > - * in 32 bits. > */ > -#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL)) > +static inline u64 mult_frac64(u64 x, u32 numer, u32 denom) > +{ > + u64 r1 = do_div(x, denom); > + u64 r2 = r1 * numer; > + > + do_div(r2, denom);
> + return (x * numer) + r2;
Parens are useless, noticed later, sorry.
Isn't mult_frac() enough here?
Btw, can you mention explicitly what is the warning you get (copy'n'paste of the line would be okay)?
> +} > > -#define SG_DEFAULT_TIMEOUT MULDIV(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ) > +#define SG_DEFAULT_TIMEOUT mult_frac64(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ) > > int sg_big_buff = SG_DEF_RESERVED_SIZE; > /* N.B. This variable is readable and writeable via > @@ -877,10 +883,10 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) > return result; > if (val < 0) > return -EIO; > - if (val >= MULDIV (INT_MAX, USER_HZ, HZ)) > - val = MULDIV (INT_MAX, USER_HZ, HZ); > + if (val >= mult_frac64(INT_MAX, USER_HZ, HZ)) > + val = mult_frac64(INT_MAX, USER_HZ, HZ);
> sfp->timeout_user = val; > - sfp->timeout = MULDIV (val, HZ, USER_HZ); > + sfp->timeout = mult_frac64(val, HZ, USER_HZ); > > return 0; > case SG_GET_TIMEOUT: /* N.B. User receives timeout as return value */ > -- > Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc. > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project > > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
-- With Best Regards, Andy Shevchenko
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