Re: [PATCH] core: Actually EIO is a fatal error

[Dmitry Monakhov <dmonakhov@openvz.org>]

On Fri, 21 Sep 2012 14:20:12 +0200, Jens Axboe <axboe@kernel.dk> wrote:
> On 09/21/2012 02:13 PM, Dmitry Monakhov wrote:
> > On Fri, 21 Sep 2012 14:00:18 +0200, Jens Axboe <axboe@kernel.dk> wrote:
> >> On 09/21/2012 01:42 PM, Dmitry Monakhov wrote:
> >>> On Fri, 21 Sep 2012 13:25:37 +0200, Jens Axboe <axboe@kernel.dk> wrote:
> >>>> On 09/21/2012 01:04 PM, Dmitry Monakhov wrote:
> >>>>> As soon as i understand this is just a mistype.
> >>>>
> >>>> It's not a typo. By that logic, EILSEQ is fatal too, since it is a
> >>>> verification failure of read data (so might as well have been an EIO).
> >>>> Fatal, in this context, means errors that fio can recover from and
> >>>> continue doing work.
> >>> Ohh i ment to say that both errors are fatal, but function called
> >>
> >> And I'm saying that NEITHER of them are fatal.
> >>
> >>> td_NON_fatal_error, and it result true in case of EIO or EILSEQ
> >>> this result continue_on_error logic broken because 
> >>> io_u.c 1440:
> >>>        if (icd->error && td_non_fatal_error(icd->error) &&
> >>>            (td->o.continue_on_error & td_error_type(io_u->ddir,
> >>>            icd->error))) {
> >>
> >> Right, so if error and error is non-fatal, we continue on that error
> >> unless told otherwise. It is logged and we continue on our business.
> > Please dint get me wrong .... but please take a look more carefully
> > 
> > Original code: ((e) == EIO || (e) == EILSEQ)
> > True for fatal errors, and false for non fatal ones
> > But function called td_NON_fatal_error()
> > And it should result opposite result
> > 
> > so my code: (!((e) == EIO || (e) == EILSEQ)) is equivalent of
> >              (err != EIO) && (err != EILSEQ)
> 
> You keep not reading my point. EIO and EILSEQ are are not fatal errors!!
> These are "expected" in the sense that we know what conditions trigger
> them.
Ok i've finally get the point. But i'm  disagree with terms
beacuse most filesystems and applications interpret EIO as fatal
error. Once device return EIO to filesystem it will fall back to RO mode
or just panic. I heard about some RAID oriented HDD which tend to return
EIO ASAP so raid controller may remap bio to another drive, but this is
very special case and such devices works only with raid controller.
From my point of view non fatal error are: ENOSPC, EBUSY, EAGAIN, ENOMEM

Nor than less it would be reasonable to make fatal error list
configurable. I'll prepare a patch sortly.

> 
> Also see the HOWTO, continue_on_error option.
> 
> -- 
> Jens Axboe
>