linux-kernel - Re: [PATCH] md: fix 32-bit build warning

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Message-ID: <876129xfqn.fsf@notabene.neil.brown.name>
Date:	Thu, 15 Oct 2015 09:11:28 +1100
From:	Neil Brown <neilb@...e.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	Goldwyn Rodrigues <rgoldwyn@...e.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] md: fix 32-bit build warning

Arnd Bergmann <arnd@...db.de> writes:

> On Monday 12 October 2015 15:59:27 Neil Brown wrote:
>> > diff --git a/drivers/md/md.c b/drivers/md/md.c
>> > index 7fff1e6884d6..e13f72a3b561 100644
>> > --- a/drivers/md/md.c
>> > +++ b/drivers/md/md.c
>> > @@ -8987,9 +8987,9 @@ static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev)
>> >  
>> >       /* recovery_cp changed */
>> >       if (le64_to_cpu(sb->resync_offset) != mddev->recovery_cp) {
>> > -             pr_info("%s:%d recovery_cp changed from %lu to %lu\n", __func__,
>> > -                             __LINE__, mddev->recovery_cp,
>> > -                             (unsigned long) le64_to_cpu(sb->resync_offset));
>> > +             pr_info("%s:%d recovery_cp changed from %llu to %llu\n", __func__,
>> > +                             __LINE__, (u64)mddev->recovery_cp,
>> > +                             (u64) le64_to_cpu(sb->resync_offset));
>> >               mddev->recovery_cp = le64_to_cpu(sb->resync_offset);
>> >       }
>> >  
>> 
>> Thanks, but is this really right?
>> I think u64 is "unsigned long" on 64bit.
>> I have always used (unsigned long long) when I want to use %llu on
>> sector_t.
>> 
>> How confident are you of using "u64" ?
>
> Very confident ;-)
>
> This used to not work until some linux-2.6 version when we changed all
> architectures to use asm-generic/int-ll64.h in the kernel, because
> a lot of code relied on printing u64 variables using %lld.
>
> I tend to use u64 for things like this because it's shorter than
> 'unsigned long long'.
>

Ahh.. good to know - thanks.

It seems that we've since removed those 'pr_info' lines, so there is
nothing to fix any more.  I'll remember that about using "u64" though -
using "unsigned long long" always felt so clumsy.

Thanks,
NeilBrown

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