kern/50423: kernel interface for reporting errors to file systems

[Thomas Klausner <wiz%NetBSD.org@localhost>]

>Number:         50423
>Category:       kern
>Synopsis:       kernel interface for reporting errors to file systems
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Fri Nov 13 15:05:00 +0000 2015
>Originator:     Thomas Klausner
>Release:        NetBSD 7.99.21
>Organization:
Curiosity is the very basis of education and if you tell me that 
curiosity killed the cat, I say only that the cat died nobly.
- Arnold Edinborough
>Environment:
	
	
Architecture: x86_64
Machine: amd64
>Description:
While Greg Oster and I were discussing RAID features, we decided it'd be
neat to have a kernel interface that could report disk or raid errors to
a file system.

The file system could then use the information from below to translate
this to errors that are meaningful to the user.

Direct reports from the disk/RAID are not as useful, since you could
have e.g. ffs-on-cgd-on-RAID, and if RAID just reports a checksum problem
in block 5100194 then the user will have no useful information at all.

>How-To-Repeat:

>Fix:
Design such a kernel interface, support it from sd/wd/raid/ccd/lvm/...
and the file systems.

>Unformatted: