Re: [PATCH] btrfs: do not clear page dirty at extent_write_cache_pages()

[Qu Wenruo <wqu@suse.com>]

在 2024/5/20 13:00, Qu Wenruo 写道:
> [PROBLEM]
> Currently we call folio_clear_dirty_for_io() for the locked dirty folio
> inside extent_write_cache_pages().
> 
> However this call is not really subpage aware, it's from the older days
> where one page can only have one sector.
> 
> But with nowadays subpage support, we can have multiple sectors inside
> one page, thus if we clear the whole page dirty flag, it would make the
> subpage and page dirty flags desynchronize.
> 
> Thankfully this is not a big deal as our current subpage routine always
> call __extent_writepage_io() for all the subpage dirty ranges, thus it
> would ensure there is no subpage range dirty left.
> 
> [FIX]
> So here we just drop the folio_clear_dirty_for_io() call, and let
> __extent_writepage_io() and extent_clear_unlock_delalloc() (which is for
> compression path) to handle the dirty page and subapge clearing.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Please drop the patch.

Weirdly with this one, generic/027 would hang on locking the page...

Thanks,
Qu
> ---
> This patch is independent from the subpage zoned fixes, thus it can be
> applied either before or after the subpage zoned fixes.
> ---
>   fs/btrfs/extent_io.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 7275bd919a3e..a8fc0fcfa69f 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2231,8 +2231,7 @@ static int extent_write_cache_pages(struct address_space *mapping,
>   				folio_wait_writeback(folio);
>   			}
>   
> -			if (folio_test_writeback(folio) ||
> -			    !folio_clear_dirty_for_io(folio)) {
> +			if (folio_test_writeback(folio)) {
>   				folio_unlock(folio);
>   				continue;
>   			}