On Mon 18-12-23 16:35:40, Christoph Hellwig wrote:
> mapping->writeback_index is only [1] used as the starting point for
> range_cyclic writeback, so there is no point in updating it for other
> types of writeback.
>
> [1] except for btrfs_defrag_file which does really odd things with
> mapping->writeback_index. But btrfs doesn't use write_cache_pages at
> all, so this isn't relevant here.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> mm/page-writeback.c | 24 ++++++++++++++----------
> 1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 7ed6c2bc8dd51c..c798c0d6d0abb4 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2403,7 +2403,6 @@ int write_cache_pages(struct address_space *mapping,
> pgoff_t index;
> pgoff_t end; /* Inclusive */
> pgoff_t done_index;
> - int range_whole = 0;
> xa_mark_t tag;
>
> folio_batch_init(&fbatch);
> @@ -2413,8 +2412,6 @@ int write_cache_pages(struct address_space *mapping,
> } else {
> index = wbc->range_start >> PAGE_SHIFT;
> end = wbc->range_end >> PAGE_SHIFT;
> - if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
> - range_whole = 1;
> }
> if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
> tag_pages_for_writeback(mapping, index, end);
> @@ -2514,14 +2511,21 @@ int write_cache_pages(struct address_space *mapping,
> }
>
> /*
> - * If we hit the last page and there is more work to be done: wrap
> - * back the index back to the start of the file for the next
> - * time we are called.
> + * For range cyclic writeback we need to remember where we stopped so
> + * that we can continue there next time we are called. If we hit the
> + * last page and there is more work to be done, wrap back to the start
> + * of the file.
> + *
> + * For non-cyclic writeback we always start looking up at the beginning
> + * of the file if we are called again, which can only happen due to
> + * -ENOMEM from the file system.
> */
> - if (wbc->range_cyclic && !done)
> - done_index = 0;
> - if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
> - mapping->writeback_index = done_index;
> + if (wbc->range_cyclic) {
> + if (done)
> + mapping->writeback_index = done_index;
> + else
> + mapping->writeback_index = 0;
> + }
>
> return ret;
> }
> --
> 2.39.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
