linux-kernel - Re: [PATCH 01/17] writeback: fix done_index when hitting the wbc->nr_to

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Message-ID: <20231219173329.wp6v4y5637wavnba@quack3>
Date: Tue, 19 Dec 2023 18:33:29 +0100
From: Jan Kara <jack@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: linux-mm@...ck.org, "Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Jan Kara <jack@...e.com>, David Howells <dhowells@...hat.com>,
	Brian Foster <bfoster@...hat.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/17] writeback: fix done_index when hitting the
 wbc->nr_to_write

On Mon 18-12-23 16:35:37, Christoph Hellwig wrote:
> When write_cache_pages finishes writing out a folio, it fails to update
> done_inde to account for the number of pages in the folio just written.
  ^^^ done_index

> That means when range_cyclic writeback is restarted, it will be
> restarted at this folio instead of after it as it should.  Fix that
> by updating done_index before breaking out of the loop.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Otherwise looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  mm/page-writeback.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index ee2fd6a6af4072..b13ea243edb6b2 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2505,6 +2505,7 @@ int write_cache_pages(struct address_space *mapping,
>  			 * keep going until we have written all the pages
>  			 * we tagged for writeback prior to entering this loop.
>  			 */
> +			done_index = folio->index + nr;
>  			wbc->nr_to_write -= nr;
>  			if (wbc->nr_to_write <= 0 &&
>  			    wbc->sync_mode == WB_SYNC_NONE) {
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR