[PATCH 4/6] mm: stop passing a writeback_control structure to __swap_writepage

[Christoph Hellwig <hch@lst.de>]

__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 2269eb9df0af..045415e2eb4f 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