swap: add swap_cache_get_folio()

Convert lookup_swap_cache() into swap_cache_get_folio() and add a
lookup_swap_cache() wrapper around it.

[akpm@linux-foundation.org: add CONFIG_SWAP=n stub for swap_cache_get_folio()]
Link: https://lkml.kernel.org/r/20220902194653.1739778-20-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/swap.h b/mm/swap.h
index 29e38f3d82d033b8d28791b4a8f91e64a4998c90..ccd8d9a9ad36dd6c8d8c6c33b71681925862182c 100644 (file)
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -39,6 +39,8 @@ 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);
+struct folio *swap_cache_get_folio(swp_entry_t entry,
+               struct vm_area_struct *vma, unsigned long addr);
 struct page *lookup_swap_cache(swp_entry_t entry,
                               struct vm_area_struct *vma,
                               unsigned long addr);
@@ -99,6 +101,12 @@ static inline int swap_writepage(struct page *p, struct writeback_control *wbc)
        return 0;
 }
 
+static inline struct folio *swap_cache_get_folio(swp_entry_t entry,
+               struct vm_area_struct *vma, unsigned long addr)
+{
+       return NULL;
+}
+
 static inline struct page *lookup_swap_cache(swp_entry_t swp,
                                             struct vm_area_struct *vma,
                                             unsigned long addr)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index a7e0438902dd11bc10f4f6c067e4ccbafa226b7f..b96bf4ec8b5b100620d4f4d60d9e9ea49a20d41e 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -317,24 +317,24 @@ static inline bool swap_use_vma_readahead(void)
 }
 
 /*
- * Lookup a swap entry in the swap cache. A found page will be returned
+ * Lookup a swap entry in the swap cache. A found folio will be returned
  * unlocked and with its refcount incremented - we rely on the kernel
- * lock getting page table operations atomic even if we drop the page
+ * lock getting page table operations atomic even if we drop the folio
  * lock before returning.
  */
-struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
-                              unsigned long addr)
+struct folio *swap_cache_get_folio(swp_entry_t entry,
+               struct vm_area_struct *vma, unsigned long addr)
 {
-       struct page *page;
+       struct folio *folio;
        struct swap_info_struct *si;
 
        si = get_swap_device(entry);
        if (!si)
                return NULL;
-       page = find_get_page(swap_address_space(entry), swp_offset(entry));
+       folio = filemap_get_folio(swap_address_space(entry), swp_offset(entry));
        put_swap_device(si);
 
-       if (page) {
+       if (folio) {
                bool vma_ra = swap_use_vma_readahead();
                bool readahead;
 
@@ -342,10 +342,10 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
                 * At the moment, we don't support PG_readahead for anon THP
                 * so let's bail out rather than confusing the readahead stat.
                 */
-               if (unlikely(PageTransCompound(page)))
-                       return page;
+               if (unlikely(folio_test_large(folio)))
+                       return folio;
 
-               readahead = TestClearPageReadahead(page);
+               readahead = folio_test_clear_readahead(folio);
                if (vma && vma_ra) {
                        unsigned long ra_val;
                        int win, hits;
@@ -366,7 +366,17 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
                }
        }
 
-       return page;
+       return folio;
+}
+
+struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
+                              unsigned long addr)
+{
+       struct folio *folio = swap_cache_get_folio(entry, vma, addr);
+
+       if (!folio)
+               return NULL;
+       return folio_file_page(folio, swp_offset(entry));
 }
 
 /**