[RFC PATCH 04/10] mm, swap: skip swap cache reclaim while storage is suspended

[Youngjun Park <youngjun.park@lge.com>]

folio_swapcache_freeable() refuses every folio for as long as
pm_suspended_storage() holds, and that covers the whole window in which
the hibernation image is written.  Every reclaim attempt the allocator
makes there drops the cluster lock, looks the folio up, trylocks it and
gives up.  swap_reclaim_full_clusters() walks a whole cluster to do it.

Stop trying.  The allocator is left with the slots that are already
free, which is all reclaim could have given it anyway.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Youngjun Park <youngjun.park@lge.com>
---
 mm/swapfile.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 07aefb782fbe..cf519c5569c4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -903,7 +903,7 @@ static bool cluster_scan_range(struct swap_info_struct *si,
 		if (swp_tb_is_null(swp_tb))
 			continue;
 		if (swp_tb_is_folio(swp_tb) && !__swp_tb_get_count(swp_tb)) {
-			if (!vm_swap_full())
+			if (!vm_swap_full() || pm_suspended_storage())
 				return false;
 			*need_reclaim = true;
 			continue;
@@ -1050,6 +1050,10 @@ static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
 	unsigned long swp_tb;
 	int nr_reclaim;
 
+	/* Swap cache cannot be freed while storage is suspended. */
+	if (pm_suspended_storage())
+		return;
+
 	if (force)
 		to_scan = swap_usage_in_pages(si) / SWAPFILE_CLUSTER;
 
@@ -1315,7 +1319,7 @@ static void swap_range_alloc(struct swap_info_struct *si,
 			     unsigned int nr_entries)
 {
 	if (swap_usage_add(si, nr_entries)) {
-		if (vm_swap_full())
+		if (vm_swap_full() && !pm_suspended_storage())
 			schedule_work(&si->reclaim_work);
 	}
 	atomic_long_sub(nr_entries, &nr_swap_pages);
-- 
2.48.1