mm, swap: rename and move some swap cluster definition and helpers

No feature change, move cluster related definitions and helpers to
mm/swap.h, also tidy up and add a "swap_" prefix for cluster lock/unlock
helpers, so they can be used outside of swap files.  And while at it, add
kerneldoc.

Link: https://lkml.kernel.org/r/20250916160100.31545-7-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 29 insertions, 68 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c3c3364cb42e..700e07cb1cbd 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -58,9 +58,6 @@ static void swap_entries_free(struct swap_info_struct *si,
 static void swap_range_alloc(struct swap_info_struct *si,
 			     unsigned int nr_entries);
 static bool folio_swapcache_freeable(struct folio *folio);
-static struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
-					      unsigned long offset);
-static inline void unlock_cluster(struct swap_cluster_info *ci);
 
 static DEFINE_SPINLOCK(swap_lock);
 static unsigned int nr_swapfiles;
@@ -258,9 +255,9 @@ again:
 	 * swap_map is HAS_CACHE only, which means the slots have no page table
 	 * reference or pending writeback, and can't be allocated to others.
 	 */
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 	need_reclaim = swap_only_has_cache(si, offset, nr_pages);
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	if (!need_reclaim)
 		goto out_unlock;
 
@@ -385,19 +382,6 @@ static void discard_swap_cluster(struct swap_info_struct *si,
 	}
 }
 
-#ifdef CONFIG_THP_SWAP
-#define SWAPFILE_CLUSTER	HPAGE_PMD_NR
-
-#define swap_entry_order(order)	(order)
-#else
-#define SWAPFILE_CLUSTER	256
-
-/*
- * Define swap_entry_order() as constant to let compiler to optimize
- * out some code if !CONFIG_THP_SWAP
- */
-#define swap_entry_order(order)	0
-#endif
 #define LATENCY_LIMIT		256
 
 static inline bool cluster_is_empty(struct swap_cluster_info *info)
@@ -425,34 +409,12 @@ static inline unsigned int cluster_index(struct swap_info_struct *si,
 	return ci - si->cluster_info;
 }
 
-static inline struct swap_cluster_info *offset_to_cluster(struct swap_info_struct *si,
-							  unsigned long offset)
-{
-	return &si->cluster_info[offset / SWAPFILE_CLUSTER];
-}
-
 static inline unsigned int cluster_offset(struct swap_info_struct *si,
 					  struct swap_cluster_info *ci)
 {
 	return cluster_index(si, ci) * SWAPFILE_CLUSTER;
 }
 
-static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si,
-						     unsigned long offset)
-{
-	struct swap_cluster_info *ci;
-
-	ci = offset_to_cluster(si, offset);
-	spin_lock(&ci->lock);
-
-	return ci;
-}
-
-static inline void unlock_cluster(struct swap_cluster_info *ci)
-{
-	spin_unlock(&ci->lock);
-}
-
 static void move_cluster(struct swap_info_struct *si,
 			 struct swap_cluster_info *ci, struct list_head *list,
 			 enum swap_cluster_flags new_flags)
@@ -808,7 +770,7 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
 	}
 out:
 	relocate_cluster(si, ci);
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	if (si->flags & SWP_SOLIDSTATE) {
 		this_cpu_write(percpu_swap_cluster.offset[order], next);
 		this_cpu_write(percpu_swap_cluster.si[order], si);
@@ -875,7 +837,7 @@ static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
 		if (ci->flags == CLUSTER_FLAG_NONE)
 			relocate_cluster(si, ci);
 
-		unlock_cluster(ci);
+		swap_cluster_unlock(ci);
 		if (to_scan <= 0)
 			break;
 	}
@@ -914,7 +876,7 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
 		if (offset == SWAP_ENTRY_INVALID)
 			goto new_cluster;
 
-		ci = lock_cluster(si, offset);
+		ci = swap_cluster_lock(si, offset);
 		/* Cluster could have been used by another order */
 		if (cluster_is_usable(ci, order)) {
 			if (cluster_is_empty(ci))
@@ -922,7 +884,7 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
 			found = alloc_swap_scan_cluster(si, ci, offset,
 							order, usage);
 		} else {
-			unlock_cluster(ci);
+			swap_cluster_unlock(ci);
 		}
 		if (found)
 			goto done;
@@ -1203,7 +1165,7 @@ static bool swap_alloc_fast(swp_entry_t *entry,
 	if (!si || !offset || !get_swap_device_info(si))
 		return false;
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 	if (cluster_is_usable(ci, order)) {
 		if (cluster_is_empty(ci))
 			offset = cluster_offset(si, ci);
@@ -1211,7 +1173,7 @@ static bool swap_alloc_fast(swp_entry_t *entry,
 		if (found)
 			*entry = swp_entry(si->type, found);
 	} else {
-		unlock_cluster(ci);
+		swap_cluster_unlock(ci);
 	}
 
 	put_swap_device(si);
@@ -1479,14 +1441,14 @@ static void swap_entries_put_cache(struct swap_info_struct *si,
 	unsigned long offset = swp_offset(entry);
 	struct swap_cluster_info *ci;
 
-	ci = lock_cluster(si, offset);
-	if (swap_only_has_cache(si, offset, nr))
+	ci = swap_cluster_lock(si, offset);
+	if (swap_only_has_cache(si, offset, nr)) {
 		swap_entries_free(si, ci, entry, nr);
-	else {
+	} else {
 		for (int i = 0; i < nr; i++, entry.val++)
 			swap_entry_put_locked(si, ci, entry, SWAP_HAS_CACHE);
 	}
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 }
 
 static bool swap_entries_put_map(struct swap_info_struct *si,
@@ -1504,7 +1466,7 @@ static bool swap_entries_put_map(struct swap_info_struct *si,
 	if (count != 1 && count != SWAP_MAP_SHMEM)
 		goto fallback;
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 	if (!swap_is_last_map(si, offset, nr, &has_cache)) {
 		goto locked_fallback;
 	}
@@ -1513,21 +1475,20 @@ static bool swap_entries_put_map(struct swap_info_struct *si,
 	else
 		for (i = 0; i < nr; i++)
 			WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE);
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 
 	return has_cache;
 
 fallback:
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 locked_fallback:
 	for (i = 0; i < nr; i++, entry.val++) {
 		count = swap_entry_put_locked(si, ci, entry, 1);
 		if (count == SWAP_HAS_CACHE)
 			has_cache = true;
 	}
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	return has_cache;
-
 }
 
 /*
@@ -1577,7 +1538,7 @@ static void swap_entries_free(struct swap_info_struct *si,
 	unsigned char *map_end = map + nr_pages;
 
 	/* It should never free entries across different clusters */
-	VM_BUG_ON(ci != offset_to_cluster(si, offset + nr_pages - 1));
+	VM_BUG_ON(ci != swp_offset_cluster(si, offset + nr_pages - 1));
 	VM_BUG_ON(cluster_is_empty(ci));
 	VM_BUG_ON(ci->count < nr_pages);
 
@@ -1652,9 +1613,9 @@ bool swap_entry_swapped(struct swap_info_struct *si, swp_entry_t entry)
 	struct swap_cluster_info *ci;
 	int count;
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 	count = swap_count(si->swap_map[offset]);
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	return !!count;
 }
 
@@ -1677,7 +1638,7 @@ int swp_swapcount(swp_entry_t entry)
 
 	offset = swp_offset(entry);
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 
 	count = swap_count(si->swap_map[offset]);
 	if (!(count & COUNT_CONTINUED))
@@ -1700,7 +1661,7 @@ int swp_swapcount(swp_entry_t entry)
 		n *= (SWAP_CONT_MAX + 1);
 	} while (tmp_count & COUNT_CONTINUED);
 out:
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	return count;
 }
 
@@ -1715,7 +1676,7 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
 	int i;
 	bool ret = false;
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 	if (nr_pages == 1) {
 		if (swap_count(map[roffset]))
 			ret = true;
@@ -1728,7 +1689,7 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
 		}
 	}
 unlock_out:
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	return ret;
 }
 
@@ -2662,8 +2623,8 @@ static void wait_for_allocation(struct swap_info_struct *si)
 	BUG_ON(si->flags & SWP_WRITEOK);
 
 	for (offset = 0; offset < end; offset += SWAPFILE_CLUSTER) {
-		ci = lock_cluster(si, offset);
-		unlock_cluster(ci);
+		ci = swap_cluster_lock(si, offset);
+		swap_cluster_unlock(ci);
 	}
 }
 
@@ -3579,7 +3540,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 	offset = swp_offset(entry);
 	VM_WARN_ON(nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER);
 	VM_WARN_ON(usage == 1 && nr > 1);
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 
 	err = 0;
 	for (i = 0; i < nr; i++) {
@@ -3634,7 +3595,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage, int nr)
 	}
 
 unlock_out:
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	return err;
 }
 
@@ -3733,7 +3694,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 
 	offset = swp_offset(entry);
 
-	ci = lock_cluster(si, offset);
+	ci = swap_cluster_lock(si, offset);
 
 	count = swap_count(si->swap_map[offset]);
 
@@ -3793,7 +3754,7 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask)
 out_unlock_cont:
 	spin_unlock(&si->cont_lock);
 out:
-	unlock_cluster(ci);
+	swap_cluster_unlock(ci);
 	put_swap_device(si);
 outer:
 	if (page)