Re: [PATCH] the dm-loop target

Christoph Hellwig
2025-03-03T15:31:59Z

On Mon, Mar 03, 2025 at 03:22:48PM +0000, Matthew Wilcox wrote:
> Funnily, I was looking at the md bitmap code too. It's the last part of
> the kernel using buffer heads with not-a-pagecache page, so it's the
> only caller of alloc_page_buffers() remaining.
>
> I think it should just use the page cache to read/write the file data,
> but I haven't looked into it in detail.

The md bitmap code is awful as it abuses it's own buffer heads in a
way that is non-coherent with the underlying fs. It should just be
using the vfs read/write helpers for in-kernel direct I/O with a
scoped nofs context.