linux-kernel - Re: [PATCH] ufs: Fix build errors on 32 bit machines

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Message-ID: <20170617182328.GV31671@ZenIV.linux.org.uk>
Date:   Sat, 17 Jun 2017 19:23:28 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Evgeniy Dushistov <dushistov@...l.ru>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] ufs: Fix build errors on 32 bit machines

On Sat, Jun 17, 2017 at 10:35:13AM -0700, Guenter Roeck wrote:
> Various 32 builds fail with error messages such as
> 
> ERROR: "__udivdi3" [fs/ufs/ufs.ko] undefined!
> 
> due to a variable type change from 32 bit to 64 bit.

Actually, that's not the only problem in that place.  The breakage
came in 2.4.14.7; the critical part was this:
            default:
-               usb1->fs_optim = SWAB32(UFS_OPTTIME);
+               usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
        
            case UFS_OPTTIME:
                request = uspi->s_fpb;
-               if (SWAB32(usb1->fs_cstotal.cs_nffree) < uspi->s_dsize *
+               if (fs32_to_cpu(sb, usb1->fs_cstotal.cs_nffree) < uspi->s_dsize *
                    (uspi->s_minfree - 2) / 100)
                        break;
-               usb1->fs_optim = SWAB32(UFS_OPTSPACE);
+               usb1->fs_optim = cpu_to_fs32(sb, UFS_OPTTIME);
                break;

See the problem?  Instead of hysteresis loop flipping between optspace and opttime
allocation policies, it *never* switches out of opttime.

That came in

commit 6293d56ca18db9ed322b2a5550ac7b27bd538cff
Author: Linus Torvalds <torvalds@...lon.transmeta.com>
Date:   Mon Feb 4 20:33:51 2002 -0800

    v2.4.14.6 -> v2.4.14.7
    
      - Jeff Garzik: network driver updates
      - Christoph Hellwig: UFS filesystem byteorder cleanups
      - me: modified Andrea VM page allocator tuning

so probably a typo in Christoph's patches, missed by everyone at the time.

And I would prefer to have the nffree levels at which we switch back and
forth precalculated at mount time.  I'll send a fix (along with those
for the last remaining xfstests failures) later today.