mm/swapfile: convert try_to_free_swap() to folio_free_swap()

Add kernel-doc for folio_free_swap() and make it return bool.  Add a
try_to_free_swap() compatibility wrapper.

Link: https://lkml.kernel.org/r/20220902194653.1739778-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 61e13d1a4caba7ebc78059bf9868adaa061ebe2a..dac6308d878e970a65bf1a35d8a9f6ecc248327f 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -490,6 +490,7 @@ static inline long get_nr_swap_pages(void)
 
 extern void si_swapinfo(struct sysinfo *);
 swp_entry_t folio_alloc_swap(struct folio *folio);
+bool folio_free_swap(struct folio *folio);
 extern void put_swap_page(struct page *page, swp_entry_t entry);
 extern swp_entry_t get_swap_page_of_type(int);
 extern int get_swap_pages(int n, swp_entry_t swp_entries[], int entry_size);
@@ -606,6 +607,11 @@ static inline swp_entry_t folio_alloc_swap(struct folio *folio)
        return entry;
 }
 
+static inline bool folio_free_swap(struct folio *folio)
+{
+       return false;
+}
+
 static inline int add_swap_extent(struct swap_info_struct *sis,
                                  unsigned long start_page,
                                  unsigned long nr_pages, sector_t start_block)

diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index e1e23b4947d73bd769bd319c821956911ff41fa6..06d47f00609b54052c0fec17345e2ab0394e9db7 100644 (file)
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -146,3 +146,10 @@ void putback_lru_page(struct page *page)
 {
        folio_putback_lru(page_folio(page));
 }
+
+#ifdef CONFIG_SWAP
+int try_to_free_swap(struct page *page)
+{
+       return folio_free_swap(page_folio(page));
+}
+#endif

diff --git a/mm/swapfile.c b/mm/swapfile.c
index e0aaeac5c829d68f4c8026988c33dbbc3052ae54..f2a446799a3939da9ba7528fb0548f60870ca3c0 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1567,43 +1567,47 @@ static bool folio_swapped(struct folio *folio)
        return swap_page_trans_huge_swapped(si, entry);
 }
 
-/*
- * If swap is getting full, or if there are no more mappings of this page,
- * then try_to_free_swap is called to free its swap space.
+/**
+ * folio_free_swap() - Free the swap space used for this folio.
+ * @folio: The folio to remove.
+ *
+ * If swap is getting full, or if there are no more mappings of this folio,
+ * then call folio_free_swap to free its swap space.
+ *
+ * Return: true if we were able to release the swap space.
  */
-int try_to_free_swap(struct page *page)
+bool folio_free_swap(struct folio *folio)
 {
-       struct folio *folio = page_folio(page);
        VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
        if (!folio_test_swapcache(folio))
-               return 0;
+               return false;
        if (folio_test_writeback(folio))
-               return 0;
+               return false;
        if (folio_swapped(folio))
-               return 0;
+               return false;
 
        /*
         * Once hibernation has begun to create its image of memory,
-        * there's a danger that one of the calls to try_to_free_swap()
+        * there's a danger that one of the calls to folio_free_swap()
         * - most probably a call from __try_to_reclaim_swap() while
         * hibernation is allocating its own swap pages for the image,
         * but conceivably even a call from memory reclaim - will free
-        * the swap from a page which has already been recorded in the
-        * image as a clean swapcache page, and then reuse its swap for
+        * the swap from a folio which has already been recorded in the
+        * image as a clean swapcache folio, and then reuse its swap for
         * another page of the image.  On waking from hibernation, the
-        * original page might be freed under memory pressure, then
+        * original folio might be freed under memory pressure, then
         * later read back in from swap, now with the wrong data.
         *
         * Hibernation suspends storage while it is writing the image
         * to disk so check that here.
         */
        if (pm_suspended_storage())
-               return 0;
+               return false;
 
        delete_from_swap_cache(folio);
        folio_set_dirty(folio);
-       return 1;
+       return true;
 }
 
 /*

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9ce6cc74d9eaed9f464af0f46f52363a901c63e8..9268e64590e4da20b7cc2d7620f2d07194b26f84 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2049,7 +2049,7 @@ activate_locked:
                if (folio_test_swapcache(folio) &&
                    (mem_cgroup_swap_full(&folio->page) ||
                     folio_test_mlocked(folio)))
-                       try_to_free_swap(&folio->page);
+                       folio_free_swap(folio);
                VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
                if (!folio_test_mlocked(folio)) {
                        int type = folio_is_file_lru(folio);