[PATCH 4/7] mm: stop passing a writeback_control structure to __swap_writepage

Christoph Hellwig
2025-05-08T05:50:03Z

__swap_writepage only needs the swap_iocb cookie from the
writeback_control structure, so pass it explicitly and remove the
now unused swap_iocb member from struct writeback_control.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
mm/page_io.c | 33 ++++++++++++++-------------------
mm/swap.h | 2 +-
mm/zswap.c | 5 +----
3 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index c420b0aa0f22..fb52bedcc966 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -281,7 +281,7 @@ int swap_writeout(struct folio *folio, struct writeback_control *wbc)
return AOP_WRITEPAGE_ACTIVATE;
}

- __swap_writepage(folio, wbc);
+ __swap_writepage(folio, wbc->swap_plug);
return 0;
out_unlock:
folio_unlock(folio);
@@ -371,9 +371,9 @@ static void sio_write_complete(struct kiocb *iocb, long ret)
mempool_free(sio, sio_pool);
}

-static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc)
+static void swap_writepage_fs(struct folio *folio, struct swap_iocb **swap_plug)
{
- struct swap_iocb *sio = NULL;
+ struct swap_iocb *sio = swap_plug ? *swap_plug : NULL;
struct swap_info_struct *sis = swp_swap_info(folio->swap);
struct file *swap_file = sis->swap_file;
loff_t pos = swap_dev_pos(folio->swap);
@@ -381,8 +381,6 @@ static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc
count_swpout_vm_event(folio);
folio_start_writeback(folio);
folio_unlock(folio);
- if (wbc->swap_plug)
- sio = *wbc->swap_plug;
if (sio) {
if (sio->iocb.ki_filp != swap_file ||
sio->iocb.ki_pos + sio->len != pos) {
@@ -401,22 +399,21 @@ static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc
bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
sio->len += folio_size(folio);
sio->pages += 1;
- if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
+ if (sio->pages == ARRAY_SIZE(sio->bvec) || !swap_plug) {
swap_write_unplug(sio);
sio = NULL;
}
- if (wbc->swap_plug)
- *wbc->swap_plug = sio;
+ if (swap_plug)
+ *swap_plug = sio;
}

static void swap_writepage_bdev_sync(struct folio *folio,
- struct writeback_control *wbc, struct swap_info_struct *sis)
+ struct swap_info_struct *sis)
{
struct bio_vec bv;
struct bio bio;

- bio_init(&bio, sis->bdev, &bv, 1,
- REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
+ bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_WRITE | REQ_SWAP);
bio.bi_iter.bi_sector = swap_folio_sector(folio);
bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);

@@ -431,13 +428,11 @@ static void swap_writepage_bdev_sync(struct folio *folio,
}

static void swap_writepage_bdev_async(struct folio *folio,
- struct writeback_control *wbc, struct swap_info_struct *sis)
+ struct swap_info_struct *sis)
{
struct bio *bio;

- bio = bio_alloc(sis->bdev, 1,
- REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
- GFP_NOIO);
+ bio = bio_alloc(sis->bdev, 1, REQ_OP_WRITE | REQ_SWAP, GFP_NOIO);
bio->bi_iter.bi_sector = swap_folio_sector(folio);
bio->bi_end_io = end_swap_bio_write;
bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
@@ -449,7 +444,7 @@ static void swap_writepage_bdev_async(struct folio *folio,
submit_bio(bio);
}

-void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
+void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug)
{
struct swap_info_struct *sis = swp_swap_info(folio->swap);

@@ -460,16 +455,16 @@ void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
* is safe.
*/
if (data_race(sis->flags & SWP_FS_OPS))
- swap_writepage_fs(folio, wbc);
+ swap_writepage_fs(folio, swap_plug);
/*
* ->flags can be updated non-atomicially (scan_swap_map_slots),
* but that will never affect SWP_SYNCHRONOUS_IO, so the data_race
* is safe.
*/
else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO))
- swap_writepage_bdev_sync(folio, wbc, sis);
+ swap_writepage_bdev_sync(folio, sis);
else
- swap_writepage_bdev_async(folio, wbc, sis);
+ swap_writepage_bdev_async(folio, sis);
}

void swap_write_unplug(struct swap_iocb *sio)
diff --git a/mm/swap.h b/mm/swap.h
index aa62463976d5..bd642078544a 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -21,7 +21,7 @@ static inline void swap_read_unplug(struct swap_iocb *plug)
}
void swap_write_unplug(struct swap_iocb *sio);
int swap_writeout(struct folio *folio, struct writeback_control *wbc);
-void __swap_writepage(struct folio *folio, struct writeback_control *wbc);
+void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug);

/* linux/mm/swap_state.c */
/* One swap address space for each 64M swap space */
diff --git a/mm/zswap.c b/mm/zswap.c
index 455e9425c5f5..3c0fd8a13718 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1070,9 +1070,6 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
struct mempolicy *mpol;
bool folio_was_allocated;
struct swap_info_struct *si;
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- };
int ret = 0;

/* try to allocate swap cache folio */
@@ -1134,7 +1131,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
folio_set_reclaim(folio);

/* start writeback */
- __swap_writepage(folio, &wbc);
+ __swap_writepage(folio, NULL);

out:
if (ret && ret != -EEXIST) {
--
2.47.2