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Message-ID: <20250514201729.48420-19-ryncsn@gmail.com>
Date: Thu, 15 May 2025 04:17:18 +0800
From: Kairui Song <ryncsn@...il.com>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>,
Hugh Dickins <hughd@...gle.com>,
Chris Li <chrisl@...nel.org>,
David Hildenbrand <david@...hat.com>,
Yosry Ahmed <yosryahmed@...gle.com>,
"Huang, Ying" <ying.huang@...ux.alibaba.com>,
Nhat Pham <nphamcs@...il.com>,
Johannes Weiner <hannes@...xchg.org>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Baoquan He <bhe@...hat.com>,
Barry Song <baohua@...nel.org>,
Kalesh Singh <kaleshsingh@...gle.com>,
Kemeng Shi <shikemeng@...weicloud.com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Ryan Roberts <ryan.roberts@....com>,
linux-kernel@...r.kernel.org,
Kairui Song <kasong@...cent.com>
Subject: [PATCH 18/28] mm, swap: rename and introduce folio_free_swap_cache
From: Kairui Song <kasong@...cent.com>
We now have folio_alloc_swap, folio_dup_swap, folio_put_swap, and
folio_free_swap (which is actually try to free). Also rename
delete_from_swap_cache to folio_free_swap_cache, because swap cache will
always be the last reference of a folio bounded entry now. Freeing the
swap cache will also attempt to free the swap entries.
Signed-off-by: Kairui Song <kasong@...cent.com>
---
mm/memory-failure.c | 2 +-
mm/memory.c | 2 +-
mm/shmem.c | 4 ++--
mm/swap.h | 14 +++++++++-----
mm/swap_state.c | 12 ------------
mm/swapfile.c | 23 +++++++++++++++++++++--
mm/zswap.c | 2 +-
7 files changed, 35 insertions(+), 24 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b91a33fb6c69..ba96aaf96e83 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1185,7 +1185,7 @@ static int me_swapcache_clean(struct page_state *ps, struct page *p)
struct folio *folio = page_folio(p);
int ret;
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
ret = delete_from_lru_cache(folio) ? MF_FAILED : MF_RECOVERED;
folio_unlock(folio);
diff --git a/mm/memory.c b/mm/memory.c
index c000e39b3eb2..a70624a55aa2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4727,7 +4727,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
*/
if (!folio_test_anon(folio)) {
WARN_ON_ONCE(folio_test_dirty(folio));
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
goto out_nomap;
}
}
diff --git a/mm/shmem.c b/mm/shmem.c
index 0d23c1c12204..c7475629365c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2123,7 +2123,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
nr_pages = folio_nr_pages(folio);
folio_wait_writeback(folio);
folio_put_swap(folio, NULL);
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
/*
* Don't treat swapin error folio as alloced. Otherwise inode->i_blocks
* won't be 0 when inode is released and thus trigger WARN_ON(i_blocks)
@@ -2365,7 +2365,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
folio_mark_accessed(folio);
folio_put_swap(folio, NULL);
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
folio_mark_dirty(folio);
put_swap_device(si);
diff --git a/mm/swap.h b/mm/swap.h
index 4c4a71081895..467996dafbae 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -151,10 +151,15 @@ extern void __swap_cache_put_entries(struct swap_info_struct *si,
*
* Swap in maps a folio in swap cache and decrease the swap table entry
* count with folio_put_swap.
+ *
+ * Swap uses lazy free, so a folio may stay in swap cache for a long time
+ * and pin the swap entry. folio_free_swap_cache and folio_free_swap can
+ * be used to reclaim the swap cache.
*/
int folio_alloc_swap(struct folio *folio, gfp_t gfp_mask);
int folio_dup_swap(struct folio *folio, struct page *subpage);
void folio_put_swap(struct folio *folio, struct page *subpage);
+void folio_free_swap_cache(struct folio *folio);
/* linux/mm/page_io.c */
int sio_pool_init(void);
@@ -226,7 +231,6 @@ static inline bool folio_swap_contains(struct folio *folio, swp_entry_t entry)
}
void show_swap_cache_info(void);
-void delete_from_swap_cache(struct folio *folio);
void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry, int nr);
struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr,
@@ -300,6 +304,10 @@ static inline void folio_put_swap(struct folio *folio, struct page *page)
{
}
+static inline void folio_free_swap_cache(struct folio *folio)
+{
+}
+
static inline void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
{
}
@@ -387,10 +395,6 @@ static inline void *swap_cache_get_shadow(swp_entry_t end)
return NULL;
}
-static inline void delete_from_swap_cache(struct folio *folio)
-{
-}
-
static inline unsigned int folio_swap_flags(struct folio *folio)
{
return 0;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 715aff5aca57..c8bb16835612 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -216,18 +216,6 @@ void __swap_cache_del_folio(swp_entry_t entry,
__swap_cache_put_entries(si, ci, entry, nr_pages);
}
-void delete_from_swap_cache(struct folio *folio)
-{
- struct swap_cluster_info *ci;
- swp_entry_t entry = folio->swap;
-
- ci = swap_lock_cluster(swp_info(entry), swp_offset(entry));
- __swap_cache_del_folio(entry, folio, NULL);
- swap_unlock_cluster(ci);
-
- folio_ref_sub(folio, folio_nr_pages(folio));
-}
-
/*
* Caller must hold a reference on the swap device, and check if the
* returned folio is still valid after locking it (e.g. folio_swap_contains).
diff --git a/mm/swapfile.c b/mm/swapfile.c
index daf7810bcb28..0a8b36ecbf08 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -273,7 +273,7 @@ static int __try_to_reclaim_swap(struct swap_info_struct *si,
if (!need_reclaim)
goto out_unlock;
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
folio_set_dirty(folio);
ret = nr_pages;
out_unlock:
@@ -1354,6 +1354,25 @@ void folio_put_swap(struct folio *folio, struct page *subpage)
swap_entries_put_map(swp_info(entry), entry, nr_pages);
}
+/*
+ * folio_free_swap_cache() - Remove the folio from swap cache, and free
+ * all entires with zero count.
+ *
+ * NOTE: if the folio is dirty and any of its swap entries' count is not
+ * zero, freeing the swap cache without write back may cause data loss.
+ */
+void folio_free_swap_cache(struct folio *folio)
+{
+ struct swap_cluster_info *ci;
+ swp_entry_t entry = folio->swap;
+
+ ci = swap_lock_cluster(swp_info(entry), swp_offset(entry));
+ __swap_cache_del_folio(entry, folio, NULL);
+ swap_unlock_cluster(ci);
+
+ folio_ref_sub(folio, folio_nr_pages(folio));
+}
+
static struct swap_info_struct *_swap_info_get(swp_entry_t entry)
{
struct swap_info_struct *si;
@@ -1787,7 +1806,7 @@ bool folio_free_swap(struct folio *folio)
if (folio_swapped(folio))
return false;
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
folio_set_dirty(folio);
return true;
}
diff --git a/mm/zswap.c b/mm/zswap.c
index 65c1aff5c4a4..6bac50bc2bf5 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1141,7 +1141,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
out:
if (ret && ret != -EEXIST) {
- delete_from_swap_cache(folio);
+ folio_free_swap_cache(folio);
folio_unlock(folio);
}
folio_put(folio);
--
2.49.0
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