Re: [PATCH v2 6/6] iomap: reduce unnecessary state_lock when setting ifs uptodate and dirty bits

Matthew Wilcox
2024-08-12T17:01:02Z

On Mon, Aug 12, 2024 at 08:11:59PM +0800, Zhang Yi wrote:
> @@ -866,9 +899,8 @@ static bool __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
> */
> if (unlikely(copied < len && !folio_test_uptodate(folio)))
> return false;
> - iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
> - iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied);
> - filemap_dirty_folio(inode->i_mapping, folio);
> +
> + iomap_set_range_dirty_uptodate(folio, from, copied);
> return true;

I wonder how often we overwrite a completely uptodate folio rather than
writing new data to a fresh folio? iow, would this be a measurable
optimisation?

if (folio_test_uptodate(folio))
iomap_set_range_dirty(folio, from, copied);
else
iomap_set_range_dirty_uptodate(folio, from, copied);