On Thu, Jul 13, 2023 at 10:55:20AM +0530, Ritesh Harjani wrote: > "Darrick J. Wong" <djwong@xxxxxxxxxx> writes: > > > [add ritesh] > > > > On Mon, Jul 10, 2023 at 02:02:49PM +0100, Matthew Wilcox (Oracle) wrote: > >> The check for the folio being under writeback is unnecessary; the caller > >> has checked this and the folio is locked, so the folio cannot be under > >> writeback at this point. > >> > >> The comment is somewhat misleading in that it talks about one specific > >> situation in which we can see a dirty folio. There are others, so change > >> the comment to explain why we can't release the iomap_page. > >> > >> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > >> Reviewed-by: Christoph Hellwig <hch@xxxxxx> > >> --- > >> fs/iomap/buffered-io.c | 9 ++++----- > >> 1 file changed, 4 insertions(+), 5 deletions(-) > >> > >> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > >> index 1cb905140528..7aa3009f907f 100644 > >> --- a/fs/iomap/buffered-io.c > >> +++ b/fs/iomap/buffered-io.c > >> @@ -483,12 +483,11 @@ bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags) > >> folio_size(folio)); > >> > >> /* > >> - * mm accommodates an old ext3 case where clean folios might > >> - * not have had the dirty bit cleared. Thus, it can send actual > >> - * dirty folios to ->release_folio() via shrink_active_list(); > >> - * skip those here. > >> + * If the folio is dirty, we refuse to release our metadata because > >> + * it may be partially dirty. Once we track per-block dirty state, > >> + * we can release the metadata if every block is dirty. > > > > Ritesh: I'm assuming that implementing this will be part of your v12 series? > > No, if it's any optimization, then I think we can take it up later too, <nod> > not in v12 please (I have been doing some extensive testing of current series). > Also let me understand it a bit more. > > @willy, > Is this what you are suggesting? So this is mainly to free up some > memory for iomap_folio_state structure then right? I think it's also to break up compound folios to free base pages or other reasons. https://lore.kernel.org/linux-xfs/20230713044326.GI108251@frogsfrogsfrogs/T/#mc83fe929d57e9aa3c1834232389cad0d62b66e7b > But then whenever we are doing a writeback, we anyway would be > allocating iomap_folio_state() and marking all the bits dirty. Isn't it > sub-optimal then? > > @@ -489,8 +489,11 @@ bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags) > * it may be partially dirty. Once we track per-block dirty state, > * we can release the metadata if every block is dirty. > */ > - if (folio_test_dirty(folio)) > + if (folio_test_dirty(folio)) { > + if (ifs_is_fully_dirty(folio, ifs)) > + iomap_page_release(folio); > return false; > + } I think it's more that we *dont* break up partially dirty folios: /* * Folio is partially dirty, do not throw away the state or * split the folio. */ if (folio_test_dirty(folio) && !ifs_is_fully_dirty(folio, ifs)) return false; /* No more private state tracking, ok to split folio. */ iomap_page_release(folio); return true; But breaking up fully dirty folios is now possible, since the mm can mark all the basepages dirty. --D > iomap_page_release(folio); > return true; > } > > (Ignore the old and new apis naming in above. It is just to get an idea) > > -ritesh > > > > > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > --D > > > >> */ > >> - if (folio_test_dirty(folio) || folio_test_writeback(folio)) > >> + if (folio_test_dirty(folio)) > >> return false; > >> iomap_page_release(folio); > >> return true; > >> -- > >> 2.39.2 > >>
