Re: [PATCH v2 4/6] iomap: correct the dirty length in page mkwrite

Darrick J. Wong
2024-08-12T16:45:36Z

On Mon, Aug 12, 2024 at 08:11:57PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
>
> When doing page mkwrite, iomap_folio_mkwrite_iter() dirty the entire
> folio by folio_mark_dirty() even the map length is shorter than one
> folio. However, on the filesystem with more than one blocks per folio,
> we'd better to only set counterpart block's dirty bit according to
> iomap_length(), so open code folio_mark_dirty() and pass the correct
> length.
>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
> fs/iomap/buffered-io.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 79031b7517e5..ac762de9a27f 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1492,7 +1492,10 @@ static loff_t iomap_folio_mkwrite_iter(struct iomap_iter *iter,
> block_commit_write(&folio->page, 0, length);
> } else {
> WARN_ON_ONCE(!folio_test_uptodate(folio));
> - folio_mark_dirty(folio);
> +
> + ifs_alloc(iter->inode, folio, 0);
> + iomap_set_range_dirty(folio, 0, length);
> + filemap_dirty_folio(iter->inode->i_mapping, folio);

Is it correct to be doing a lot more work by changing folio_mark_dirty
to filemap_dirty_folio? Now pagefaults call __mark_inode_dirty which
they did not before. Also, the folio itself must be marked dirty if any
of the ifs bitmap is marked dirty, so I don't understand the change
here.

--D

> }
>
> return length;
> --
> 2.39.2
>
>