On Mon, Jun 18, 2018 at 5:37 PM, Andrew Lutomirski <l...@mit.edu> wrote:
>> On Jun 18, 2018, at 3:54 PM, Chris Murphy <li...@colorremedies.com> wrote:


>> Getting journal support in the bootloader isn't going to happen. I've
>> already talked to the various fs upstreams about it.
>>
>
> Why are you talking to the fs upstreams?  The problem is a bug in
> GRUB, full stop.

OK so you're going to blame uboot and syslinux and others for not
supporting JBD2 and journal replay as well? I disagree that its worth
the effort.

> All this freeze crap that Fedora does is just
> papering over the bug.

Yeah I don't like any of that either, and in retrospect I should not
have bought off on the idea. But that's getting off topic.

>IMO the right thing to do is to get *GRUB*
> upstream to have a fully functional implementation of *one*
> widely-supported fs.  Hmm, GRUB supports F2FS, and F2FS is
> log-structured, right?  So I don't see how GRUB could fail to read a
> dirty filesystem correctly even if it wanted to.

Journaled file systems have the journal bolted on. It's a completely
different beast. To read any structure, there must be code. There's
simply no code to read the XFS or ext3/4 log. It appears there was an
attempt to get GRUB (and I think it's GRUB legacy) to support JBD2 but
it was abandoned. I don't know the history.


> Or someone could design a very simple, highly reliable, filesystem
> designed to make it easy to do atomic-enough updates and to read
> reliably.  Think VFAT-like but with a full atomic swap of all FS
> metadata.  Or a dead-simple log-structured FS.  /me ducks.
>
> Seriously, though, F2FS might be a fantastic choice for this purpose.

UDF might be doable with multisession acting to ensure atomic
operations, but that seems like a lot of work. If UEFI had gone UDF
instead of FAT, it'd be a different story.

F2FS might be sane. I rather like the idea of Fedora IoT leveraging F2FS.

>> So add that to the list of packages that need an ESP syncing daemon if
>> they don't want to be responsible for dynamically mounting and
>> umounting the ESP.

Fair enough.

-- 
Chris Murphy
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