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Wed, 14 May 2025 13:19:11 -0700 (PDT) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Matthew Wilcox , Hugh Dickins , Chris Li , David Hildenbrand , Yosry Ahmed , "Huang, Ying" , Nhat Pham , Johannes Weiner , Baolin Wang , Baoquan He , Barry Song , Kalesh Singh , Kemeng Shi , Tim Chen , Ryan Roberts , linux-kernel@vger.kernel.org, Kairui Song Subject: [PATCH 18/28] mm, swap: rename and introduce folio_free_swap_cache Date: Thu, 15 May 2025 04:17:18 +0800 Message-ID: <20250514201729.48420-19-ryncsn@gmail.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250514201729.48420-1-ryncsn@gmail.com> References: <20250514201729.48420-1-ryncsn@gmail.com> Reply-To: Kairui Song Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kairui Song 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 --- 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