On Wed, Aug 25, 2021 at 12:02 PM Rasmus Villemoes
[off-list ref] wrote:

On 25/08/2021 08.32, Christoph Hellwig wrote:

quoted

On Tue, Aug 24, 2021 at 03:44:48PM -0400, Theodore Ts'o wrote:

quoted

The problem is whether we use struct head_page, or folio, or mempages,
we're going to be subsystem users' faces.  And people who are using it
every day will eventually get used to anything, whether it's "folio"
or "xmoqax", we sould give a thought to newcomers to Linux file system
code.  If they see things like "read_folio()", they are going to be
far more confused than "read_pages()" or "read_mempages()".

Are they?  It's not like page isn't some randomly made up term
as well, just one that had a lot more time to spread.

quoted

So if someone sees "kmem_cache_alloc()", they can probably make a
guess what it means, and it's memorable once they learn it.
Similarly, something like "head_page", or "mempages" is going to a bit
more obvious to a kernel newbie.  So if we can make a tiny gesture
towards comprehensibility, it would be good to do so while it's still
easier to change the name.

All this sounds really weird to me.  I doubt there is any name that
nicely explains "structure used to manage arbitrary power of two
units of memory in the kernel" very well.  So I agree with willy here,
let's pick something short and not clumsy.  I initially found the folio
name a little strange, but working with it I got used to it quickly.
And all the other uggestions I've seen s far are significantly worse,
especially all the odd compounds with page in it.

A comment from the peanut gallery: I find the name folio completely
appropriate and easy to understand. Our vocabulary is already strongly
inspired by words used in the world of printed text: the smallest unit
of information is a char(acter) [ok, we usually call them bytes], a few
characters make up a word, there's a number of words to each (cache)
line, and a number of those is what makes up a page. So obviously a
folio is something consisting of a few pages.

Are the analogies perfect? Of course not. But they are actually quite
apt; words, lines and pages don't universally have one size, but they do
form a natural hierarchy describing how we organize information.

Splitting a word across lines can slow down the reader so should be
avoided... [sorry, couldn't resist].

And if we ever want to manage page cache using an arbitrary number
of contiguous filios, we can always saw them into a scroll ;-)

Thanks,
Amir.