Re: [PATCH 01/15] ubifs: Set page uptodate in the correct place

Zhihao Cheng
2024-01-22T07:23:12Z

在 2024/1/21 7:08, Matthew Wilcox (Oracle) 写道:
> Page cache reads are lockless, so setting the freshly allocated page
> uptodate before we've overwritten it with the data it's supposed to have
> in it will allow a simultaneous reader to see old data. Move the call
> to SetPageUptodate into ubifs_write_end(), which is after we copied the
> new data into the page.
>
> Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
> Cc: stable@vger.kernel.org
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> fs/ubifs/file.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> index 5029eb3390a5..40a9b03ef821 100644
> --- a/fs/ubifs/file.c
> +++ b/fs/ubifs/file.c
> @@ -463,9 +463,6 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
> return err;
> }
> }
> -
> - SetPageUptodate(page);
> - ClearPageError(page);
> }

This solution looks good to me, and I think 'SetPageUptodate' should be
removed from write_begin_slow(slow path) too.

>
> err = allocate_budget(c, page, ui, appending);
> @@ -569,6 +566,9 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
> goto out;
> }
>
> + if (len == PAGE_SIZE)
> + SetPageUptodate(page);
> +
> if (!PagePrivate(page)) {
> attach_page_private(page, (void *)1);
> atomic_long_inc(&c->dirty_pg_cnt);