On Thu 31-07-25 17:21:26, Joanne Koong wrote:
> Add filemap_dirty_folio_pages() which takes in the number of pages to dirty.
>
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
...
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index b0ae10a6687d..a3805988f3ad 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2732,7 +2732,7 @@ void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb)
> * try_to_free_buffers() to fail.
> */
> void __folio_mark_dirty(struct folio *folio, struct address_space *mapping,
> - int warn, long nr_pages)
> + int warn, long nr_pages, bool newly_dirty)
> {
> unsigned long flags;
>
> @@ -2740,12 +2740,29 @@ void __folio_mark_dirty(struct folio *folio, struct address_space *mapping,
> if (folio->mapping) { /* Race with truncate? */
> WARN_ON_ONCE(warn && !folio_test_uptodate(folio));
> folio_account_dirtied(folio, mapping, nr_pages);
> - __xa_set_mark(&mapping->i_pages, folio_index(folio),
> - PAGECACHE_TAG_DIRTY);
> + if (newly_dirty)
> + __xa_set_mark(&mapping->i_pages, folio_index(folio),
> + PAGECACHE_TAG_DIRTY);
> }
> xa_unlock_irqrestore(&mapping->i_pages, flags);
I think this is a dangerous coding pattern. What is making sure that by the
time you get here newly_dirty is still valid? I mean the dirtying can race
e.g. with writeback and so it can happen that the page is clean by the time
we get here but newly_dirty is false. We are often protected by page lock
when dirtying a folio but not always... So if nothing else this requires a
careful documentation about correct use.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
