mm/khugepaged: try to free transhuge swapcache when possible

Transhuge swapcaches won't be freed in __collapse_huge_page_copy().  It's
because release_pte_page() is not called for these pages and thus
free_page_and_swap_cache can't grab the page lock.  These pages won't be
freed from swap cache even if we are the only user until next time
reclaim.  It shouldn't hurt indeed, but we could try to free these pages
to save more memory for system.

Link: https://lkml.kernel.org/r/20220625092816.4856-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 95a5b7aa1ae990e357b54c0d61ec6d6f06b04fad..6d11c51b2b627503522158cd6cadd0041ecddc10 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -455,6 +455,7 @@ static inline unsigned long total_swapcache_pages(void)
        return global_node_page_state(NR_SWAPCACHE);
 }
 
+extern void free_swap_cache(struct page *page);
 extern void free_page_and_swap_cache(struct page *);
 extern void free_pages_and_swap_cache(struct page **, int);
 /* linux/mm/swapfile.c */
@@ -539,6 +540,10 @@ static inline void put_swap_device(struct swap_info_struct *si)
 /* used to sanity check ptes in zap_pte_range when CONFIG_SWAP=0 */
 #define free_swap_and_cache(e) is_pfn_swap_entry(e)
 
+static inline void free_swap_cache(struct page *page)
+{
+}
+
 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 {
        return 0;

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 08e885f28def15791ce9a594ad1235ee3edcf02f..01e0d6336754ece59f91a05eea787828f0ecf6a6 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -755,7 +755,12 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
 
        list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
                list_del(&src_page->lru);
-               release_pte_page(src_page);
+               mod_node_page_state(page_pgdat(src_page),
+                                   NR_ISOLATED_ANON + page_is_file_lru(src_page),
+                                   -compound_nr(src_page));
+               unlock_page(src_page);
+               free_swap_cache(src_page);
+               putback_lru_page(src_page);
        }
 }
 

diff --git a/mm/swap.h b/mm/swap.h
index fa0816af47121c44f5e51152afa156ff8338b0e6..17936e068c1c8fab4dfc652705a813ab5a4d1af5 100644 (file)
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -41,7 +41,6 @@ void __delete_from_swap_cache(struct folio *folio,
 void delete_from_swap_cache(struct folio *folio);
 void clear_shadow_from_swap_cache(int type, unsigned long begin,
                                  unsigned long end);
-void free_swap_cache(struct page *page);
 struct page *lookup_swap_cache(swp_entry_t entry,
                               struct vm_area_struct *vma,
                               unsigned long addr);
@@ -81,10 +80,6 @@ static inline struct address_space *swap_address_space(swp_entry_t entry)
        return NULL;
 }
 
-static inline void free_swap_cache(struct page *page)
-{
-}
-
 static inline void show_swap_cache_info(void)
 {
 }