On Mon, 18 Sept 2023 at 12:32, Jiri Kosina <jikos@xxxxxxxxxx> wrote:
>
> I am afraid this is not reflecting reality.
>
> I am pretty sure that "give me that document on a USB stick, and I'll take
> a look" leads to using things like libreoffice (or any other editor liked
> by general public) to open the file directly on the FAT USB stick. And
> that's pretty much guaranteed to use mmap().
Ugh. I would have hoped that anybody will fall back to read/write -
because we definitely have filesystems that don't support mmap.
But I guess they are so specialized as to not ever trigger that kind
of problem (eg /proc - nobody is putting office documents there ;)
A cache-incoherent MAP_PRIVATE only mmap (ie one that doesn't react to
'write()' changing the data) is easy to do, but yeah, it would still
be a lot more work than just "keep things as-is".
Linus
