Re: [MAINTAINERS/KERNEL SUMMIT] Trust and maintenance of file systems

H. Peter Anvin
2023-09-18T20:33:53Z

On September 18, 2023 12:32:05 PM PDT, Jiri Kosina <jikos@kernel.org> wrote:
>On Mon, 18 Sep 2023, Linus Torvalds wrote:
>
>> But mmap() is *not* important for a filesystem that is used just for
>> data transport. I bet that FAT is still widely used, for example, and
>> while exFAT is probably making inroads, I suspect most of us have used a
>> USB stick with a FAT filesystem on it in the not too distant past. Yet I
>> doubt we'd have ever even noticed if 'mmap' didn't work on FAT. Because
>> all you really want for data transport is basic read/write support.
>
>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().
>

I mean... fopen() on Linux optionally uses mmap()... and it used to do so unconditionally, even. mmap() is a good match for stdio (at least the input side), so it is a reasonable thing to do.