Re: EXT FS support

[Laszlo Ersek <lersek@redhat.com>]

On 11/24/16 02:03, Rebecca Cran wrote:
> On 11/23/16 1:11 PM, Laszlo Ersek wrote:
> 
>>>> Separately, a small note on ext4 (because you mention it above). I
>>>> seem to recall a filesystem expert colleague of mine advise
>>>> *against* using journaled filesystems for booting with e.g. grub2.
>>>> The argument goes (if I recall right), XFS is considered to be in
>>>> clean state if the data has made it to the final location *or* the
>>>> persistent journal. When you cleanly unmount (or remount r/o) and
>>>> shut down, the journal will be flushed to the final location, so a
>>>> boot loader that doesn't know about the journal will read consistent
>>>> data. However, if you crash *without* data loss, then part of the
>>>> data might be in the journal only, and only clients that can read
>>>> the journal will see consistent data.
>>>>
>>>>> This might or might not be
>>>>> an issue, depending on what the point of the exercise is.
> 
> 
> The problem of course is that "reset" (reboot), "reset -s" (shutdown)
> etc. don't have any hooks a driver can use to flush data, so there will
> sometimes (depending on how long ago data was written) be an unclean
> unmount. At least when booting an OS there's an ExitBootServices event
> available to make sure any data is flushed before boot services ends.

Related: https://bugzilla.tianocore.org/show_bug.cgi?id=224

> Though I've seen one person talking about how there at least used to be
> a bug that means ExitBootServices isn't/wasn't called for one OS.
>