"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,
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?
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;
+ }
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
>>
