2024-02-03 08:35:17

by Christoph Hellwig

Subject: [PATCH 13/13] writeback: Remove a use of write_cache_pages() from do_writepages()

From: "Matthew Wilcox (Oracle)" <[email protected]>

Use the new writeback_iter() directly instead of indirecting
through a callback.

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
[hch: ported to the while based iter style]
Signed-off-by: Christoph Hellwig <[email protected]>
---
mm/page-writeback.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5fe4cdb7dbd61a..53ff2d8219ddb6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2577,13 +2577,25 @@ int write_cache_pages(struct address_space *mapping,
}
EXPORT_SYMBOL(write_cache_pages);

-static int writepage_cb(struct folio *folio, struct writeback_control *wbc,
- void *data)
+static int writeback_use_writepage(struct address_space *mapping,
+ struct writeback_control *wbc)
{
- struct address_space *mapping = data;
- int ret = mapping->a_ops->writepage(&folio->page, wbc);
- mapping_set_error(mapping, ret);
- return ret;
+ struct folio *folio = NULL;
+ struct blk_plug plug;
+ int err;
+
+ blk_start_plug(&plug);
+ while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
+ err = mapping->a_ops->writepage(&folio->page, wbc);
+ mapping_set_error(mapping, err);
+ if (err == AOP_WRITEPAGE_ACTIVATE) {
+ folio_unlock(folio);
+ err = 0;
+ }
+ }
+ blk_finish_plug(&plug);
+
+ return err;
}

int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
@@ -2599,12 +2611,7 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
if (mapping->a_ops->writepages) {
ret = mapping->a_ops->writepages(mapping, wbc);
} else if (mapping->a_ops->writepage) {
- struct blk_plug plug;
-
- blk_start_plug(&plug);
- ret = write_cache_pages(mapping, wbc, writepage_cb,
- mapping);
- blk_finish_plug(&plug);
+ ret = writeback_use_writepage(mapping, wbc);
} else {
/* deal with chardevs and other special files */
ret = 0;
--
2.39.2

2024-02-05 11:54:53

by Jan Kara

Subject: Re: [PATCH 13/13] writeback: Remove a use of write_cache_pages() from do_writepages()

On Sat 03-02-24 08:11:47, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <[email protected]>
>
> Use the new writeback_iter() directly instead of indirecting
> through a callback.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
> [hch: ported to the while based iter style]
> Signed-off-by: Christoph Hellwig <[email protected]>

Looks good. Feel free to add:

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

I've just noticed one preexisting problem which was made more visible by
your reshuffling:

> +static int writeback_use_writepage(struct address_space *mapping,
> + struct writeback_control *wbc)
> {
> - struct address_space *mapping = data;
> - int ret = mapping->a_ops->writepage(&folio->page, wbc);
> - mapping_set_error(mapping, ret);
> - return ret;
> + struct folio *folio = NULL;
> + struct blk_plug plug;
> + int err;
> +
> + blk_start_plug(&plug);
> + while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
> + err = mapping->a_ops->writepage(&folio->page, wbc);
> + mapping_set_error(mapping, err);

So if ->writepage() returns AOP_WRITEPAGE_ACTIVATE, we shouldn't call
mapping_set_error() because that's just going to confuse the error
tracking.

> + if (err == AOP_WRITEPAGE_ACTIVATE) {
> + folio_unlock(folio);
> + err = 0;
> + }
> + }
> + blk_finish_plug(&plug);
> +
> + return err;
> }

Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR

2024-02-05 15:48:43

by Brian Foster

Subject: Re: [PATCH 13/13] writeback: Remove a use of write_cache_pages() from do_writepages()

On Sat, Feb 03, 2024 at 08:11:47AM +0100, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <[email protected]>
>
> Use the new writeback_iter() directly instead of indirecting
> through a callback.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
> [hch: ported to the while based iter style]
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---

LGTM, modulo Jan's comments:

Reviewed-by: Brian Foster <[email protected]>

> mm/page-writeback.c | 31 +++++++++++++++++++------------
> 1 file changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 5fe4cdb7dbd61a..53ff2d8219ddb6 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2577,13 +2577,25 @@ int write_cache_pages(struct address_space *mapping,
> }
> EXPORT_SYMBOL(write_cache_pages);
>
> -static int writepage_cb(struct folio *folio, struct writeback_control *wbc,
> - void *data)
> +static int writeback_use_writepage(struct address_space *mapping,
> + struct writeback_control *wbc)
> {
> - struct address_space *mapping = data;
> - int ret = mapping->a_ops->writepage(&folio->page, wbc);
> - mapping_set_error(mapping, ret);
> - return ret;
> + struct folio *folio = NULL;
> + struct blk_plug plug;
> + int err;
> +
> + blk_start_plug(&plug);
> + while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
> + err = mapping->a_ops->writepage(&folio->page, wbc);
> + mapping_set_error(mapping, err);
> + if (err == AOP_WRITEPAGE_ACTIVATE) {
> + folio_unlock(folio);
> + err = 0;
> + }
> + }
> + blk_finish_plug(&plug);
> +
> + return err;
> }
>
> int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
> @@ -2599,12 +2611,7 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
> if (mapping->a_ops->writepages) {
> ret = mapping->a_ops->writepages(mapping, wbc);
> } else if (mapping->a_ops->writepage) {
> - struct blk_plug plug;
> -
> - blk_start_plug(&plug);
> - ret = write_cache_pages(mapping, wbc, writepage_cb,
> - mapping);
> - blk_finish_plug(&plug);
> + ret = writeback_use_writepage(mapping, wbc);
> } else {
> /* deal with chardevs and other special files */
> ret = 0;
> --
> 2.39.2
>