Re: [PATCH v2 2/4] mm: vmalloc: use rwsem, mutex for vmap_area_lock and vmap_block->lock

Matthew Wilcox
2023-03-24T05:32:09Z

On Fri, Mar 24, 2023 at 04:25:39PM +1100, Dave Chinner wrote:
> Did you read the comment above this function? I mean, it's all about
> how poorly kvmalloc() works for the highly concurrent, fail-fast
> context that occurs in the journal commit fast path, and how we open
> code it with kmalloc and vmalloc to work "ok" in this path.
>
> Then if you go look at the commits related to it, you might find
> that XFS developers tend to write properly useful changelogs to
> document things like "it's better, but vmalloc will soon have lock
> contention problems if we hit it any harder"....

The problem with writing whinges like this is that mm developers don't
read XFS changelogs. I certainly had no idea this was a problem, and
I doubt anybody else who could make a start at fixing this problem had
any idea either. Why go to all this effort instead of sending an email
to linux-mm?