[PATCH 5/7] mm: stop passing a writeback_control structure to swap_writeout

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

swap_writeout only needs the swap_iocb cookie from the writeback_control
structure, so pass it explicitly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/writeback.h | 7 -------
mm/page_io.c | 4 ++--
mm/shmem.c | 10 +---------
mm/swap.h | 4 +++-
mm/vmscan.c | 10 +---------
5 files changed, 7 insertions(+), 28 deletions(-)

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 82f217970092..9e960f2faf79 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -72,13 +72,6 @@ struct writeback_control {
*/
unsigned no_cgroup_owner:1;

- /* To enable batching of swap writes to non-block-device backends,
- * "plug" can be set point to a 'struct swap_iocb *'. When all swap
- * writes have been submitted, if with swap_iocb is not NULL,
- * swap_write_unplug() should be called.
- */
- struct swap_iocb **swap_plug;
-
/* internal fields used by the ->writepages implementation: */
struct folio_batch fbatch;
pgoff_t index;
diff --git a/mm/page_io.c b/mm/page_io.c
index fb52bedcc966..a2056a5ecb13 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -237,7 +237,7 @@ static void swap_zeromap_folio_clear(struct folio *folio)
* We may have stale swap cache pages in memory: notice
* them here and get rid of the unnecessary final write.
*/
-int swap_writeout(struct folio *folio, struct writeback_control *wbc)
+int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug)
{
int ret = 0;

@@ -281,7 +281,7 @@ int swap_writeout(struct folio *folio, struct writeback_control *wbc)
return AOP_WRITEPAGE_ACTIVATE;
}

- __swap_writepage(folio, wbc->swap_plug);
+ __swap_writepage(folio, swap_plug);
return 0;
out_unlock:
folio_unlock(folio);
diff --git a/mm/shmem.c b/mm/shmem.c
index 941b9b29e78a..2033d2e3d35d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1635,21 +1635,13 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug,
list_add(&info->swaplist, &shmem_swaplist);

if (!folio_alloc_swap(folio, __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN)) {
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .nr_to_write = SWAP_CLUSTER_MAX,
- .range_start = 0,
- .range_end = LLONG_MAX,
- .for_reclaim = 1,
- .swap_plug = plug,
- };
shmem_recalc_inode(inode, 0, nr_pages);
swap_shmem_alloc(folio->swap, nr_pages);
shmem_delete_from_page_cache(folio, swp_to_radix_entry(folio->swap));

mutex_unlock(&shmem_swaplist_mutex);
BUG_ON(folio_mapped(folio));
- return swap_writeout(folio, &wbc);
+ return swap_writeout(folio, plug);
}

list_del_init(&info->swaplist);
diff --git a/mm/swap.h b/mm/swap.h
index bd642078544a..c6d661fa9db7 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -3,6 +3,8 @@
#define _MM_SWAP_H

struct mempolicy;
+struct swap_iocb;
+
extern int page_cluster;

#ifdef CONFIG_SWAP
@@ -20,7 +22,7 @@ static inline void swap_read_unplug(struct swap_iocb *plug)
__swap_read_unplug(plug);
}
void swap_write_unplug(struct swap_iocb *sio);
-int swap_writeout(struct folio *folio, struct writeback_control *wbc);
+int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug);
void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug);

/* linux/mm/swap_state.c */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index fea78f01d04e..ad89b36eba01 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -655,14 +655,6 @@ typedef enum {
static pageout_t writeout(struct folio *folio, struct address_space *mapping,
struct swap_iocb **plug, struct list_head *folio_list)
{
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- .nr_to_write = SWAP_CLUSTER_MAX,
- .range_start = 0,
- .range_end = LLONG_MAX,
- .for_reclaim = 1,
- .swap_plug = plug,
- };
int res;

folio_set_reclaim(folio);
@@ -675,7 +667,7 @@ static pageout_t writeout(struct folio *folio, struct address_space *mapping,
if (shmem_mapping(mapping))
res = shmem_writeout(folio, plug, folio_list);
else
- res = swap_writeout(folio, &wbc);
+ res = swap_writeout(folio, plug);

if (res < 0)
handle_write_error(mapping, folio, res);
--
2.47.2