On Thu 14-12-23 14:25:34, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
>
> Instead of having a 'done' variable that controls the nested loops,
> have a writeback_finish() that can be returned directly. This involves
> keeping more things in writeback_control, but it's just moving stuff
> allocated on the stack to being allocated slightly earlier on the stack.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> [hch: reorder and comment struct writeback_control]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> include/linux/writeback.h | 8 +++++
> mm/page-writeback.c | 72 +++++++++++++++++++++------------------
> 2 files changed, 46 insertions(+), 34 deletions(-)
>
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index 083387c00f0c8b..05e8add4b5ae3c 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -11,6 +11,7 @@
> #include <linux/flex_proportions.h>
> #include <linux/backing-dev-defs.h>
> #include <linux/blk_types.h>
> +#include <linux/pagevec.h>
>
> struct bio;
>
> @@ -40,6 +41,7 @@ enum writeback_sync_modes {
> * in a manner such that unspecified fields are set to zero.
> */
> struct writeback_control {
> + /* public fields that can be set and/or consumed by the caller: */
> long nr_to_write; /* Write this many pages, and decrement
> this for each page written */
> long pages_skipped; /* Pages which were not written */
> @@ -77,6 +79,12 @@ struct writeback_control {
> */
> struct swap_iocb **swap_plug;
>
> + /* internal fields used by the ->writepages implementation: */
> + struct folio_batch fbatch;
> + pgoff_t done_index;
> + int err;
> + unsigned range_whole:1; /* entire file */
Do we really need the range_whole member here? It is trivially derived from
range_start && range_end and used only in one place in writeback_finish().
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index ee2fd6a6af4072..45309f3b8193f8 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2360,6 +2360,24 @@ void tag_pages_for_writeback(struct address_space *mapping,
> }
> EXPORT_SYMBOL(tag_pages_for_writeback);
>
> +static int writeback_finish(struct address_space *mapping,
> + struct writeback_control *wbc, bool done)
> +{
> + folio_batch_release(&wbc->fbatch);
> +
> + /*
> + * If we hit the last page and there is more work to be done:
> + * wrap the index back to the start of the file for the next
> + * time we are called.
> + */
> + if (wbc->range_cyclic && !done)
> + wbc->done_index = 0;
> + if (wbc->range_cyclic || (wbc->range_whole && wbc->nr_to_write > 0))
> + mapping->writeback_index = wbc->done_index;
> +
> + return wbc->err;
> +}
Also I suspect we can get rid of the 'done' argument here. After all it
just controls whether we cycle back to index 0 which we could just
determine as:
if (wbc->range_cyclic && !wbc->err && wbc->nr_to_write > 0) {
WARN_ON_ONCE(wbc->sync_mode != WB_SYNC_NONE);
wbc->done_index = 0;
}
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
