Re: [PATCH v3 03/16] iomap: refactor the writeback interface

Christoph Hellwig
2025-07-03T12:17:00Z

On Wed, Jul 02, 2025 at 10:13:53AM -0700, Darrick J. Wong wrote:
> > + int (*writeback_range)(struct iomap_writepage_ctx *wpc,
> > + struct folio *folio, u64 pos, unsigned int len, u64 end_pos);
>
> Why does @pos change from loff_t to u64 here? Are we expecting
> filesystems that set FOP_UNSIGNED_OFFSET?

It doesn't really change, it matches what iomap_writepage_map_blocks
was doing. I guess it simply doesn't fix the existing inconsistency.

> > + int (*submit_ioend)(struct iomap_writepage_ctx *wpc, int status);
>
> Nit: ^^ indenting change here.

Yeah, RST formatting is a mess unfortunately. I think the problem is
that the exiting code uses 4 space indents. I wonder if that's required
by %##% RST?

> > + if (wpc->iomap.type != IOMAP_HOLE)
> > + *wb_pending = true;
>
> /me wonders if this should be an outparam of ->writeback_range to signal
> that it actually added the folio to the writeback ioend chain? Or maybe
> just a boolean in iomap_writepage_ctx that we clear before calling
> ->writeback_range and iomap_add_to_ioend can set it as appropriate?

What's the benefit of that? A hole pretty clearly signal there is
no writeback here.

> Should this jump label should be named add_to_ioend or something? We
> already mapped the blocks. The same applies to the zoned version of
> this function.

The newer version already uses a map_blocks helper for both again.