linux-kernel - Re: POSIX violation by writeback error

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Message-ID: <CAJDTihyhA7Q_O=DhdPxLquReY1CO=3y3XgZtZ5pA5kY+DTAvMg@mail.gmail.com>
Date:   Tue, 4 Sep 2018 18:45:54 +0800
From:   焦晓冬 <milestonejxd@...il.com>
To:     R.E.Wolff@...wizard.nl
Cc:     jlayton@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: POSIX violation by writeback error

On Tue, Sep 4, 2018 at 5:29 PM Rogier Wolff <R.E.Wolff@...wizard.nl> wrote:
>
> On Tue, Sep 04, 2018 at 04:58:59PM +0800, 焦晓冬 wrote:
>
> > As for suggestion, maybe the error flag of inode/mapping, or the entire inode
> > should not be evicted if there was an error. That hopefully won't take much
> > memory. On extreme conditions, where too much error inode requires staying
> > in memory, maybe we should panic rather then spread the error.
>
> Again you are hoping it will fit in memory. In an extreme case it
> won't fit in memory. Tyring to come up with heuristics about when to
> remember and when to forget such things from the past is very
> difficult.

The key point is to report errors, not to hide it from user space to
prevent further errors/damage,
and that is also what POSIX wants.

And, storing inode/mapping/error_flag in memory is quite different
from storing the data itself.
They are tiny and only increase per inode rather than per error page.
>
> Think of my comments as: "it's harder than you think", not as "can't
> be done".
>
>         Roger.
>
> --
> ** R.E.Wolff@...Wizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 **
> **    Delftechpark 26 2628 XH  Delft, The Netherlands. KVK: 27239233    **
> *-- BitWizard writes Linux device drivers for any device you may have! --*
> The plan was simple, like my brother-in-law Phil. But unlike
> Phil, this plan just might work.