Hi,
On Fri, Mar 26, 2021 at 6:41 AM Andrew Price <anpr...@redhat.com> wrote:
>
> On 25/03/2021 17:58, Alexander Aring wrote:
> > This patch removes a note that the barrier option is automatically turned
> > off if the underlaying device doesn't support I/O barriers. So far I
> > understand it's default on, means "barriers" option is applied which
> > should not make any problems if the underlaying device supports something
> > or not. There is by the kernel or gfs2-utils no automatically detection
> > going on which changes this mount option.
>
> Hm, should there be automatic detection? Has there ever been? I'd like
> to get to the bottom of why this language is here before removing it.
>
no idea if there was ever an auto detection or there exists currently
one. I didn't find any auto detection during my research. The related
part came in by: 06b5fb87 ("gfs2: man page updates"). My understanding
is that this option is default "barrier" and you should do "nobarrier"
in cases when you know what you are doing. I even don't know if such
automatic detection is possible, the man-page says "(e.g. its on a
UPS, or it doesn't have a write cache)" in regards to block devices. I
think there is no way in the kernel/user space to check if the block
device is behind a UPS. Maybe there exists some in user space over
hdparm but then things need to be right connected? Regarding cache
handling, you need to know a lot about the used architecture.
I am not sure here as well. I was reading about such automatic
detection and wanted to see how it's done with the result: there is no
auto detection (in gfs2(kernel)/gfs2-utils software)?
- Alex
