linux-kernel - Re: Cache coherency bug: stale reads on /dev/sda1

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Message-ID: <CA+jjjYT6+NJwB2Kn0jWLKtmz3dWH6UnVJNA6vDbPXnnJnHMf9Q@mail.gmail.com>
Date:   Sat, 26 Aug 2023 18:25:58 -0700
From:   Joshua Hudson <joshudson@...il.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux IDE and libata <linux-ide@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>,
        Damien Le Moal <dlemoal@...nel.org>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Subject: Re: Cache coherency bug: stale reads on /dev/sda1

I am presuming you mean "Are you sure this not a hardware issue?"

I am sure it is not, for two reasons.

1) If it were a hardware issue I would still expect the two device
nodes (whole disk and partition) to report the *same* data.

2) I have since developed a workaround involving BLKFLSDEV. The
workaround is really ugly.

On Sat, Aug 26, 2023 at 6:03 PM Bagas Sanjaya <bagasdotme@...il.com> wrote:
>
> On Sat, Aug 26, 2023 at 02:59:45PM -0700, Joshua Hudson wrote:
> > uname -a
> > Linux nova 6.4.12 #1 SMP PREEMPT_DYNAMIC Sat Aug 26 09:11:27 PDT 2023
> > x86_64 GNU/Linux
> >
> > Kernel source is
> > https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/linux-6.4.12.tar.xz
> >
> > Can reliably reproduce as follows:
> >
> > # hexedit /dev/sda1 (this is my EFI partition)
> > PgDn
> > # hexedit /dev/sda
> > G 100000  (your value may vary--we want to seek to the start of the
> > EFI partition)
> > PgDn
> > PgDn
> > ^C
> > write a marker to the padding between the BPB and the first FAT sector.
> > (If your system doesn't have one, edit an error message in the boot sector)
> > ^X
> > # hexedit /dev/sda1
> > PgDn
> > Look for marker written above, find it's not there !!!
> > ^C
> >
> > I discovered this one trying to defragment my EFI partition after a
> > grub upgrade left it very fragmented due to replacing logos.
>
> Are you sure this is hardware issue?
>
> --
> An old man doll... just what I always wanted! - Clara