Re: [PATCH] ext4: cancel dirty accounting for folios without buffers

[Zhu Jia]

Hi Yi,

Thanks for taking a look.

Yes, clearing PAGECACHE_TAG_DIRTY/TOWRITE would make the page-cache state
cleaner. I had a version that did this by adding a helper around
folio_cancel_dirty() and clearing the xarray tags after confirming the
folio was still the same clean page-cache entry.

It looked like this:

static void ext4_cancel_dirty_folio(struct address_space *mapping,
				    struct folio *folio)
{
	XA_STATE(xas, &mapping->i_pages, folio->index);
	unsigned long flags;

	folio_cancel_dirty(folio);

	xas_lock_irqsave(&xas, flags);
	if (xas_load(&xas) == folio && !folio_test_dirty(folio)) {
		xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY);
		xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE);
	}
	xas_unlock_irqrestore(&xas, flags);
}

The reason I left the tags unchanged in this version is that I was not sure
whether it is appropriate for ext4 to open-code xarray tag cleanup directly.

If you think this is the right direction, I can add the helper back and
send a v2.

Thanks,
Jia