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

[Christoph Hellwig <hch@lst.de>]

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.