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mm, swap: move common swap cache operations into standalone helpers

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Move a few swap cache checking, adding, and deletion operations into
standalone helpers to be used later.  And while at it, add proper kernel
doc.

No feature or behavior change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-2-88ae43e064c7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kairui Song
2026-06-02 15:22:21 -07:00
committed by Andrew Morton
parent a2e61ffb47
commit bebee474c1
1 changed files with 100 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mm/swap_state.c
+100 -46
View File
@@ -137,8 +137,47 @@ void *swap_cache_get_shadow(swp_entry_t entry)
return NULL;
}
void __swap_cache_add_folio(struct swap_cluster_info *ci,
struct folio *folio, swp_entry_t entry)
/**
* __swap_cache_add_check - Check if a range is suitable for adding a folio.
* @ci: The locked swap cluster.
* @ci_off: Range start offset.
* @nr: Number of slots to check.
* @shadow: Returns the shadow value if one exists in the range.
*
* Check if all slots covered by given range have a swap count >= 1.
* Retrieves the shadow if there is one.
*
* Context: Caller must lock the cluster.
* Return: 0 if success, error code if failed.
*/
static int __swap_cache_add_check(struct swap_cluster_info *ci,
unsigned int ci_off, unsigned int nr,
void **shadow)
{
unsigned int ci_end = ci_off + nr;
unsigned long old_tb;
lockdep_assert_held(&ci->lock);
if (WARN_ON_ONCE(ci_off >= SWAPFILE_CLUSTER))
return -EINVAL;
if (unlikely(!ci->table))
return -ENOENT;
do {
old_tb = __swap_table_get(ci, ci_off);
if (unlikely(swp_tb_is_folio(old_tb)))
return -EEXIST;
if (unlikely(!__swp_tb_get_count(old_tb)))
return -ENOENT;
if (swp_tb_is_shadow(old_tb))
*shadow = swp_tb_to_shadow(old_tb);
} while (++ci_off < ci_end);
return 0;
}
static void __swap_cache_do_add_folio(struct swap_cluster_info *ci,
struct folio *folio, swp_entry_t entry)
{
unsigned int ci_off = swp_cluster_offset(entry), ci_end;
unsigned long nr_pages = folio_nr_pages(folio);
@@ -159,7 +198,28 @@ void __swap_cache_add_folio(struct swap_cluster_info *ci,
folio_ref_add(folio, nr_pages);
folio_set_swapcache(folio);
folio->swap = entry;
}
/**
* __swap_cache_add_folio - Add a folio to the swap cache and update stats.
* @ci: The locked swap cluster.
* @folio: The folio to be added.
* @entry: The swap entry corresponding to the folio.
*
* Unconditionally add a folio to the swap cache. The caller must ensure
* all slots are usable and have no conflicts. This assigns entry to
* @folio->swap, increases folio refcount by the number of pages, and
* updates swap cache stats.
*
* Context: Caller must ensure the folio is locked and lock the cluster
* that holds the entries.
*/
void __swap_cache_add_folio(struct swap_cluster_info *ci,
struct folio *folio, swp_entry_t entry)
{
unsigned long nr_pages = folio_nr_pages(folio);
__swap_cache_do_add_folio(ci, folio, entry);
node_stat_mod_folio(folio, NR_FILE_PAGES, nr_pages);
lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr_pages);
}
@@ -168,9 +228,11 @@ void __swap_cache_add_folio(struct swap_cluster_info *ci,
* swap_cache_add_folio - Add a folio into the swap cache.
* @folio: The folio to be added.
* @entry: The swap entry corresponding to the folio.
* @gfp: gfp_mask for XArray node allocation.
* @shadowp: If a shadow is found, return the shadow.
*
* Add a folio into the swap cache. Will return error if any slot is no
* longer a valid swapped out slot or already occupied by another folio.
*
* Context: Caller must ensure @entry is valid and protect the swap device
* with reference count or locks.
*/
@@ -179,60 +241,31 @@ static int swap_cache_add_folio(struct folio *folio, swp_entry_t entry,
{
int err;
void *shadow = NULL;
unsigned long old_tb;
unsigned int ci_off;
struct swap_info_struct *si;
struct swap_cluster_info *ci;
unsigned int ci_start, ci_off, ci_end;
unsigned long nr_pages = folio_nr_pages(folio);
si = __swap_entry_to_info(entry);
ci_start = swp_cluster_offset(entry);
ci_end = ci_start + nr_pages;
ci_off = ci_start;
ci = swap_cluster_lock(si, swp_offset(entry));
if (unlikely(!ci->table)) {
err = -ENOENT;
goto failed;
ci_off = swp_cluster_offset(entry);
err = __swap_cache_add_check(ci, ci_off, nr_pages, &shadow);
if (err) {
swap_cluster_unlock(ci);
return err;
}
do {
old_tb = __swap_table_get(ci, ci_off);
if (unlikely(swp_tb_is_folio(old_tb))) {
err = -EEXIST;
goto failed;
}
if (unlikely(!__swp_tb_get_count(old_tb))) {
err = -ENOENT;
goto failed;
}
if (swp_tb_is_shadow(old_tb))
shadow = swp_tb_to_shadow(old_tb);
} while (++ci_off < ci_end);
__swap_cache_add_folio(ci, folio, entry);
swap_cluster_unlock(ci);
if (shadowp)
*shadowp = shadow;
return 0;
failed:
swap_cluster_unlock(ci);
return err;
return 0;
}
/**
* __swap_cache_del_folio - Removes a folio from the swap cache.
* @ci: The locked swap cluster.
* @folio: The folio.
* @entry: The first swap entry that the folio corresponds to.
* @shadow: shadow value to be filled in the swap cache.
*
* Removes a folio from the swap cache and fills a shadow in place.
* This won't put the folio's refcount. The caller has to do that.
*
* Context: Caller must ensure the folio is locked and in the swap cache
* using the index of @entry, and lock the cluster that holds the entries.
*/
void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio,
swp_entry_t entry, void *shadow)
static void __swap_cache_do_del_folio(struct swap_cluster_info *ci,
struct folio *folio,
swp_entry_t entry, void *shadow)
{
int count;
unsigned long old_tb;
@@ -259,14 +292,12 @@ void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio,
folio_swapped = true;
else
need_free = true;
/* If shadow is NULL, we sets an empty shadow. */
/* If shadow is NULL, we set an empty shadow. */
__swap_table_set(ci, ci_off, shadow_to_swp_tb(shadow, count));
} while (++ci_off < ci_end);
folio->swap.val = 0;
folio_clear_swapcache(folio);
node_stat_mod_folio(folio, NR_FILE_PAGES, -nr_pages);
lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr_pages);
if (!folio_swapped) {
__swap_cluster_free_entries(si, ci, ci_start, nr_pages);
@@ -279,6 +310,29 @@ void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio,
}
}
/**
* __swap_cache_del_folio - Removes a folio from the swap cache.
* @ci: The locked swap cluster.
* @folio: The folio.
* @entry: The first swap entry that the folio corresponds to.
* @shadow: shadow value to be filled in the swap cache.
*
* Removes a folio from the swap cache and fills a shadow in place.
* This won't put the folio's refcount. The caller has to do that.
*
* Context: Caller must ensure the folio is locked and in the swap cache
* using the index of @entry, and lock the cluster that holds the entries.
*/
void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio,
swp_entry_t entry, void *shadow)
{
unsigned long nr_pages = folio_nr_pages(folio);
__swap_cache_do_del_folio(ci, folio, entry, shadow);
node_stat_mod_folio(folio, NR_FILE_PAGES, -nr_pages);
lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr_pages);
}
/**
* swap_cache_del_folio - Removes a folio from the swap cache.
* @folio: The folio.