linux-kernel - Re: next-20210511 - btrfs build failure on arm

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Date:   Tue, 11 May 2021 20:09:52 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Valdis Klētnieks <valdis.kletnieks@...edu>
Cc:     Qu Wenruo <wqu@...e.com>, David Sterba <dsterba@...e.com>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>
Subject: Re: next-20210511 - btrfs build failure on arm

On Tue, May 11, 2021 at 02:08:02PM -0400, Valdis Klētnieks wrote:
> An arm allmodconfig build died with:
> 
> ERROR: modpost: "__aeabi_uldivmod" [fs/btrfs/btrfs.ko] undefined!
> 
> Some digging around with nm and looking at the assembler points at:
> 
> @ /usr/src/linux-next/fs/btrfs/extent_io.c:2676:        const int nr_bits = (end + 1 - start) / fs_info->sectorsize_bits;
>         adds    r1, r1, #1      @, tmp552, 
>         adc     r0, r0, #0      @, tmp551, 
>         ldr     r3, [r5, #1576] @ tmp2, _47->sectorsize_bits
>         bl      __aeabi_uldivmod                @       
> 
> Introduced by this commit:
> 
> commit 6512659d8f13015dccfb38a13c6d117d22572019
> Author: Qu Wenruo <wqu@...e.com>
> Date:   Mon May 3 10:08:55 2021 +0800
> 
>     btrfs: submit read time repair only for each corrupted sector
> 
> Looks like that line could use something from include/linux/math.h

We got another report already, there's division instead of shift (a
mistake), so the expression would require u64/u32 division. The correct
one is (end + 1 - start) >> fs_info->sectorsize_bits; and will be fixed
in upcoming next.