nfs: skip bootpc when vfs.root.mountfrom is other than nfs
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Authored by alfredo on Apr 29 2022, 9:22 PM.

Details

Reviewers

sjg
glebius
gonzo
imp
rmacklem

Commits

rG4e6cf9ee5808: nfs: skip bootpc when vfs.root.mountfrom is other than nfs
rG3cb9f1976c26: nfs: skip bootpc when vfs.root.mountfrom is other than nfs

Summary

If "vfs.root.mountfrom" is set and the value is something other
than "nfs:*", it means the user doesn't want to mount root via nfs,
there's no reason to continue with bootpc

The powerpcspe kernel (MPC85XXSPE), compiled with BOOTP_NFSROOT
by default, gets stuck on bootpc/dhcp request loop when no DHCP
server is available on the network, even when user specifies a
local disk via "vfs.root.mountfrom" kernel parameter.

MFC after: 2 weeks
Sponsored by: Instituto de Pesquisas Eldorado (eldorado.org.br)

Test Plan

test powerpcspe kernel under QEMU:

with "vfs.root.mountfrom" set to NFS
with "vfs.root.mountfrom" set to local partition (virtio-scsi)
without "vfs.root.mountfrom" and DHCP server on network
without "vfs.root.mountfrom" and without DHCP server on network

Diff Detail

Repository

rG FreeBSD src repository

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Unit

Tests Not Applicable

Event Timeline

alfredo created this revision.Apr 29 2022, 9:22 PM

Herald added subscribers: Contributor Reviews (src), imp. · View Herald TranscriptApr 29 2022, 9:22 PM

alfredo requested review of this revision.Apr 29 2022, 9:22 PM

Harbormaster completed remote builds in B45434: Diff 105574.Apr 29 2022, 9:22 PM

alfredo edited the test plan for this revision. (Show Details)Apr 29 2022, 9:41 PM

alfredo added a reviewer: rmacklem.

alfredo added a project: PowerPC.

Herald added subscribers: luporl, bdragon. · View Herald TranscriptApr 29 2022, 9:41 PM

sjg added a subscriber: sjg.Apr 29 2022, 11:41 PM

sjg added inline comments.

sys/nfs/bootp_subr.c
1537	Where might `nfs:` appear if not at the start of the string?

Beyond changing strstr() to a check for "nfs:" at the beginning of the
string, as suggested by sjg@, I don't see a problem with this.

However, I do not do diskless booting or know anything about
how vfs.root.mountroot is used, so I do not feel qualified to
review this. Maybe sjg@ could do so?

use strncmp instead of strstr in order to match only the beginning of the string

Harbormaster completed remote builds in B45448: Diff 105626.May 2 2022, 11:56 AM

alfredo added a reviewer: sjg.May 2 2022, 11:56 AM

updated, thanks!

@rmacklem, 'vfs.root.mountroot' is used as a kernel parameter to specify (or override) where is the root filesystem to be mounted and its partition type. It's usually something like "vfs.root.mountroot=ufs:/dev/da0s1a" if you use a local disk, or "vfs.root.mountroot=nfs:192.168.0.1:/tftpboot/root" if using nfs.

It really needs someone familiar with bootstrapping to review this.
(Except for being the nfs case, it really has nothing to do with nfs.)

alfredo added reviewers: glebius, gonzo, imp.May 5 2022, 7:08 PM

I think this is fine as is.
There's no need to check for nfs in the middle of a string, unless there's some use case I'm unaware of...