On 2023/10/10 22:21, Ryan Roberts wrote:
As preparation for supporting small-sized THP in the swap-out path,
without first needing to split to order-0, Remove the CLUSTER_FLAG_HUGE,
which, when present, always implies PMD-sized THP, which is the same as
the cluster size.
The only use of the flag was to determine whether a swap entry refers to
a single page or a PMD-sized THP in swap_page_trans_huge_swapped().
Instead of relying on the flag, we now pass in nr_pages, which
originates from the folio's number of pages. This allows the logic to
work for folios of any order.
The one snag is that one of the swap_page_trans_huge_swapped() call
sites does not have the folio. But it was only being called there to
avoid bothering to call __try_to_reclaim_swap() in some cases.
__try_to_reclaim_swap() gets the folio and (via some other functions)
calls swap_page_trans_huge_swapped(). So I've removed the problematic
call site and believe the new logic should be equivalent.
Removing CLUSTER_FLAG_HUGE also means we can remove split_swap_cluster()
which used to be called during folio splitting, since
split_swap_cluster()'s only job was to remove the flag.
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
include/linux/swap.h | 10 ----------
mm/huge_memory.c | 3 ---
mm/swapfile.c | 47 ++++++++------------------------------------
3 files changed, 8 insertions(+), 52 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 19f30a29e1f1..a073366a227c 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -259,7 +259,6 @@ struct swap_cluster_info {
};
#define CLUSTER_FLAG_FREE 1 /* This cluster is free */
#define CLUSTER_FLAG_NEXT_NULL 2 /* This cluster has no next cluster */
-#define CLUSTER_FLAG_HUGE 4 /* This cluster is backing a transparent huge page */
/*
* We assign a cluster to each CPU, so each CPU can allocate swap entry from
@@ -595,15 +594,6 @@ static inline int add_swap_extent(struct swap_info_struct *sis,
}
#endif /* CONFIG_SWAP */
-#ifdef CONFIG_THP_SWAP
-extern int split_swap_cluster(swp_entry_t entry);
-#else
-static inline int split_swap_cluster(swp_entry_t entry)
-{
- return 0;
-}
-#endif
-
#ifdef CONFIG_MEMCG
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c9cbcbf6697e..46b3fb943207 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2597,9 +2597,6 @@ static void __split_huge_page(struct page *page, struct list_head *list,
shmem_uncharge(head->mapping->host, nr_dropped);
remap_page(folio, nr);
- if (folio_test_swapcache(folio))
- split_swap_cluster(folio->swap);
-
for (i = 0; i < nr; i++) {
struct page *subpage = head + i;
if (subpage == page)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e52f486834eb..c668838fa660 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -342,18 +342,6 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
info->data = 0;
}
-static inline bool cluster_is_huge(struct swap_cluster_info *info)
-{
- if (IS_ENABLED(CONFIG_THP_SWAP))
- return info->flags & CLUSTER_FLAG_HUGE;
- return false;
-}
-
-static inline void cluster_clear_huge(struct swap_cluster_info *info)
-{
- info->flags &= ~CLUSTER_FLAG_HUGE;
-}
-
static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
unsigned long offset)
{
@@ -1021,7 +1009,7 @@ static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot)
offset = idx * SWAPFILE_CLUSTER;
ci = lock_cluster(si, offset);
alloc_cluster(si, idx);
- cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE);
+ cluster_set_count_flag(ci, SWAPFILE_CLUSTER, 0);
Maybe just use cluster_set_count() and kill cluster_set_count_flag().
