linux-kernel - Re: After KUnit update for Linux 5.15-rc1 - unable to share VFAT filesystem via samba

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Message-ID: <CAFd5g46N6PuOrEyaqK4jRx1_NyVqgtPWvRc2=8vQ8xu2iS3Low@mail.gmail.com>
Date:   Fri, 10 Sep 2021 14:23:16 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Arthur Marsh <arthur.marsh@...ernode.on.net>,
        David Gow <davidgow@...gle.com>
Cc:     skhan@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: After KUnit update for Linux 5.15-rc1 - unable to share VFAT
 filesystem via samba

+David Gow - just FYI since you are the only KUnit person who touched
VFAT. PTAL at other emails in thread too, please.

On Fri, Sep 10, 2021 at 4:57 AM Arthur Marsh
<arthur.marsh@...ernode.on.net> wrote:
>
>
>  Hi, I have been sharing an old VFAT formatted hard disk on one pc to
> another using Samba and sometime after kernel 5.14.0 it stopped working (apparently no longer being shared as the mount.smbfs command
> on the client failed with error -13 yet mount.smbfs still worked for
> ext3 filesytems shared from the same machine which had the VFAT
> filesystem).
>  The only error I saw on the machine with the VFAT formatted hard disk
> was the output of the mount command had truncated the name of the
> mount to only include the first 4 characters of the base name of the
> mount point.
>  e.g. when VFAT filesystem was mounted on /mnt/victoria, the output of
> the mount command showed the filesytem mounted on /mnt/vict
>
> The kernel build used was i386 with gcc 11.2.0-4 using
>
> make - j2 menuconfig bindeb-pkg
>
> .config available on request.
>
>  The git-bisect was:
> victoria:/usr/src/linux# git bisect loggit bisect start '--' 'fs/fat'#
> good: [7d2a07b769330c34b4deabeed939325c77a7ec2f] Linux 5.14git bisect
> good 7d2a07b769330c34b4deabeed939325c77a7ec2f# bad:
> [a3fa7a101dcff93791d1b1bdb3affcad1410c8c1] Merge branches 'akpm' and
> 'akpm-hotfixes' (patches from Andrew)git bisect bad
> a3fa7a101dcff93791d1b1bdb3affcad1410c8c1# good:
> [edb0872f44ec9976ea6d052cb4b93cd2d23ac2ba] block: move the bdi from
> the request_queue to the gendiskgit bisect good
> edb0872f44ec9976ea6d052cb4b93cd2d23ac2ba# good:
> [b0d4adaf3b3c4402d9c3b6186e02aa1e4f7985cd] fat: Add KUnit tests for
> checksums and timestampsgit bisect good
> b0d4adaf3b3c4402d9c3b6186e02aa1e4f7985cd# bad:
> [c815f04ba94940fbc303a6ea9669e7da87f8e77d] Merge tag
> 'linux-kselftest-kunit-5.15-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftestgit
> bisect bad c815f04ba94940fbc303a6ea9669e7da87f8e77d# first bad commit:
> [c815f04ba94940fbc303a6ea9669e7da87f8e77d] Merge tag
> 'linux-kselftest-kunit-5.15-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest
>
> amarsh04@...toria:~$ mount|grep vic/dev/sdb6 on /vict type vfat
> (rw,relatime,uid=65534,gid=65534,fmask=0000,dmask=0000,allow_utime=0022,codepage=437,iocharset=utf8,shortname=mixed,errors=remount-ro)

I don't see how our patch could have caused this either. Nevertheless,
I CC'ed David who has worked on VFAT who may be able to provide more
info.

> Happy to run any further tests but kernel builds are slow on this machine (Pentium Dl.
>
> Arthur.