CVS commit: [tls-maxphys] src/sys/dev/raidframe

["Thor Lancelot Simon" <tls%netbsd.org@localhost>]

Module Name:    src
Committed By:   tls
Date:           Wed Oct 17 01:36:13 UTC 2012

Modified Files:
        src/sys/dev/raidframe [tls-maxphys]: rf_netbsdkintf.c

Log Message:
Add a minphys routine for raidframe.

For now, we will address the problem of someone adding, at runtime with
a filesystem mounted, a drive to an existing RAID set, that drive being
on a different controller or bus such that it has a smaller maximum
transfer size than the smallest such size of any component previously
in the set, by clamping RAIDframe's reported maximum transfer size at
the old MAXPHYS value multiplied by the number of data disks in the
set.

In the future, we could either implement transfer-splitting to
the device specific maxphys in a generic way for all disks (Manuel's
proposal, and probably the best solution) or simply forbid adding
new components to RAID sets while running if those new components
have a smaller maxphys than that of any component already in the set
(my proposal; less flexible but a lot less code to write).

Anyway, now you should be able to see your 5 disk RAID5 set do
256k transfers through the filesystem -- 64k per component
instead of 64K total.  A win!


To generate a diff of this commit:
cvs rdiff -u -r1.298 -r1.298.2.1 src/sys/dev/raidframe/rf_netbsdkintf.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.