On Sun, 17 Sept 2023 at 11:58, Theodore Ts'o <tytso@xxxxxxx> wrote:
>
> Ext4 uses buffer_heads, and wasn't on your list because we don't use
> sb_bread().
Heh. Look closer at my list. ext4 actually was on my list, and it
turns out that's just because 'sb_bread()' is still mentioned in a
comment.
I did say that my list wasn't really the result of any exhaustive
analysis, but I picked up ext4 by luck.
And yes, ext4 was also one of the reasons I then mentioned that within
the contexts of individual filesystems, it may make sense to deprecate
the use of buffer heads.
Because yes, buffer heads _are_ old and overly simplistic. And I don't
really disagree with people who don't want to extend on them any more.
There are better models.
I think buffer heads are great for one thing, and really one thing
only: legacy use cases.
So I don't think it should be a shock to anybody that most of the
listed filesystems are random old legacy cases (or related to such -
exfat).
But "old" does not mean "bad". And legacy in many ways is worth
cherishing. It needs to become a whole lot more painful than buffer
heads have ever been to be a real issue.
It is in fact somewhat telling that of that list of odds and ends
there was *one* filesystem that was mentioned in this thread that is
actively being deprecated (and happens to use buffer heads).
And that filesystem has been explicitly not maintained, and is being
deprecated partly exactly because it is the opposite of cherished. So
the pain isn't worth it.
All largely for some rather obvious non-technical reasons.
So while reiserfs was mentioned as some kind of "good model for
deprecation", let's be *real* here. The reason nobody wants to have
anything to do with reiserfs is that Hans Reiser murdered his wife.
And I really *really* hope nobody takes that to heart as a good model
for filesystem deprecation.
Linus
