Re: [PATCH] the dm-loop target

Kent Overstreet
2025-03-13T16:33:44Z

On Thu, Mar 13, 2025 at 05:21:36PM +0100, Mikulas Patocka wrote:
> > IS_SWAPFILE isn't going way, as can't allow other writers to it.
> > Also asides from the that the layouts are fairly complex.
> >
> > The right way ahead for swap is to literally just treat it as a slightly
> > special case of direct I/o that is allowed to IS_SWAPFILE files. We
> > can safely do writeback to file backed folios under memory pressure,
> > so we can also go through the normal file system path.
>
> But that is prone to low-memory-deadlock because the filesystems allocate
> buffer memory when they are mapping logical blocks to physical blocks. You
> would need to have a mempool in the filesystems, so that they can make
> forward progress even if there is no memory free - and that would
> complicate them.

I can't speak for everone else, but bcachefs has those mempools.