Re: URE, link resets, user hostile defaults

[Phil Turmel <philip@turmel.org>]

On 06/28/2016 01:33 PM, Chris Murphy wrote:

> Perhaps there's a better way to do this than change the default
> timeout in the kernel? Maybe what we need is an upstream udev rule
> that polls SCT ERC for each drive, and if it's
> disabled/unsupported/unknown then it sets a much higher command timer
> for that block device. And maybe it only does this on USB and SATA.
> For anything enterprise or NAS grade, they do report (at least to
> smartctl) SCT ERC in deciseconds. The most common value is 70
> deciseconds, so a 30 second command timer is OK. Maybe it could even
> be lower but that's a separate optimization conversation.

When Neil retired from maintainership, I mentioned that I would take a
stab at this.  You're right, just setting the kernel default timeout to
180 would be a regression.  If I recall correctly, there are network
services that would disconnect if storage stacks could delay that long
before replying, whether good or bad.

So a device discovery process that examines the drive's parameter pages
and makes an intelligent decision would be the way to go.  But as you
can see, I haven't dug into the ata & scsi layers to figure it out yet.
 It won't hurt my feelings if someone beats me to it.

Phil