[PATCH 1/8] mm: Factor find_get_swap_page out of mincore_page

Matthew Wilcox (Oracle)
2020-08-19T18:48:43Z

Provide this functionality from the swap cache. It's useful for
more than just mincore().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/swap.h | 7 +++++++
mm/mincore.c | 28 ++--------------------------
mm/swap_state.c | 31 +++++++++++++++++++++++++++++++
3 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 661046994db4..247527ea3e66 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -427,6 +427,7 @@ extern void free_pages_and_swap_cache(struct page **, int);
extern struct page *lookup_swap_cache(swp_entry_t entry,
struct vm_area_struct *vma,
unsigned long addr);
+struct page *find_get_swap_page(struct address_space *mapping, pgoff_t index);
extern struct page *read_swap_cache_async(swp_entry_t, gfp_t,
struct vm_area_struct *vma, unsigned long addr,
bool do_poll);
@@ -569,6 +570,12 @@ static inline struct page *lookup_swap_cache(swp_entry_t swp,
return NULL;
}

+static inline
+struct page *find_get_swap_page(struct address_space *mapping, pgoff_t index)
+{
+ return find_get_page(mapping, index);
+}
+
static inline int add_to_swap(struct page *page)
{
return 0;
diff --git a/mm/mincore.c b/mm/mincore.c
index 453ff112470f..2806258f99c6 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -48,7 +48,7 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
* and is up to date; i.e. that no page-in operation would be required
* at this time if an application were to map and access this page.
*/
-static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
+static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
{
unsigned char present = 0;
struct page *page;
@@ -59,31 +59,7 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
* any other file mapping (ie. marked !present and faulted in with
* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
*/
-#ifdef CONFIG_SWAP
- if (shmem_mapping(mapping)) {
- page = find_get_entry(mapping, pgoff);
- /*
- * shmem/tmpfs may return swap: account for swapcache
- * page too.
- */
- if (xa_is_value(page)) {
- swp_entry_t swp = radix_to_swp_entry(page);
- struct swap_info_struct *si;
-
- /* Prevent swap device to being swapoff under us */
- si = get_swap_device(swp);
- if (si) {
- page = find_get_page(swap_address_space(swp),
- swp_offset(swp));
- put_swap_device(si);
- } else
- page = NULL;
- }
- } else
- page = find_get_page(mapping, pgoff);
-#else
- page = find_get_page(mapping, pgoff);
-#endif
+ page = find_get_swap_page(mapping, index);
if (page) {
present = PageUptodate(page);
put_page(page);
diff --git a/mm/swap_state.c b/mm/swap_state.c
index c16eebb81d8b..986b4e3d3bad 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -414,6 +414,37 @@ struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
return page;
}

+/**
+ * find_get_swap_page - Find and get a page from the page or swap caches.
+ * @mapping: The address_space to search.
+ * @index: The page cache index.
+ *
+ * This is like find_get_page(), but if we find a swap entry for
+ * shmem/tmpfs, we also look in the swap cache for the page.
+ *
+ * Return: The found page or %NULL.
+ */
+struct page *find_get_swap_page(struct address_space *mapping, pgoff_t index)
+{
+ swp_entry_t swp;
+ struct swap_info_struct *si;
+ struct page *page = find_get_entry(mapping, index);
+
+ if (!xa_is_value(page))
+ return page;
+ if (!shmem_mapping(mapping))
+ return NULL;
+
+ swp = radix_to_swp_entry(page);
+ /* Prevent swapoff from happening to us */
+ si = get_swap_device(swp);
+ if (!si)
+ return NULL;
+ page = find_get_page(swap_address_space(swp), swp_offset(swp));
+ put_swap_device(si);
+ return page;
+}
+
struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr,
bool *new_page_allocated)
--
2.28.0