Re: [QUESTION] xfs, iomap: Handle writeback errors to prevent silent data corruption

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Tue, 2025-06-03 at 07:41 -0700, Christoph Hellwig wrote:
> [taking this private to discuss the mpt drivers]
> 
> > Hmmm... DID_SOFT_ERROR... Normally, this is an immediate retry as
> > this normally is used to indicate that a command is a collateral
> > abort due to an NCQ error, and per ATA spec, that command should be
> > retried. However, the *BAD* thing about Broadcom HBAs using this is
> > that it increments the command retry counter, so if a command ends
> > up being retried more than 5 times due to other commands failing,
> > the command runs out of retries and is failed like this. The
> > command retry counter should *not* be incremented for NCQ
> > collateral aborts. I tried to fix this, but it is impossible as we
> > actually do not know if this is a collateral abort or something
> > else. The HBA events used to handle completion do not allow
> > differentiation. Waiting on Broadcom to do something about this
> > (the mpi3mr HBA driver has the same nasty issue).
> 
> Maybe we should just change the mpt3 sas/mr drivers to use
> DID_SOFT_ERROR less?  In fact there's not really a whole lot of
> DID_SOFT_ERROR users otherwise, and there's probably better status
> codes whatever they are doing can be translated to that do not
> increment the retry counter.

The status code that does that (retry without incrementing the counter)
is DID_IMM_RETRY.  The driver has to be a bit careful about using this
because we can get into infinite retry loops.

Regards,

James