2023-12-18 15:36:47

by Christoph Hellwig

Subject: [PATCH 01/17] writeback: fix done_index when hitting the wbc->nr_to_write

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.
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 <[email protected]>
---
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

2023-12-19 17:33:40

by Jan Kara

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 <[email protected]>

Otherwise looks good. Feel free to add:

Reviewed-by: Jan Kara <[email protected]>

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 <[email protected]>
SUSE Labs, CR