mm: add swap cache interface for swap reference
In a following patch, the usage of swap cache is recorded into swap_map.
This patch is for necessary interface changes to do that.
2 interfaces:
- swapcache_prepare()
- swapcache_free()
are added for allocating/freeing refcnt from swap-cache to existing swap
entries. But implementation itself is not changed under this patch. At
adding swapcache_free(), memcg's hook code is moved under
swapcache_free(). This is better than using scattered hooks.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index f30c069..259e96c 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -282,8 +282,10 @@
extern swp_entry_t get_swap_page(void);
extern swp_entry_t get_swap_page_of_type(int);
extern int swap_duplicate(swp_entry_t);
+extern int swapcache_prepare(swp_entry_t);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern void swap_free(swp_entry_t);
+extern void swapcache_free(swp_entry_t, struct page *page);
extern int free_swap_and_cache(swp_entry_t);
extern int swap_type_of(dev_t, sector_t, struct block_device **);
extern unsigned int count_swap_pages(int, int);
@@ -352,11 +354,16 @@
#define free_swap_and_cache(swp) is_migration_entry(swp)
#define swap_duplicate(swp) is_migration_entry(swp)
+#define swapcache_prepare(swp) is_migration_entry(swp)
static inline void swap_free(swp_entry_t swp)
{
}
+static inline void swapcache_free(swp_entry_t swp, struct page *page)
+{
+}
+
static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr)
{
diff --git a/mm/shmem.c b/mm/shmem.c
index 0132fbd..47ab191 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1097,7 +1097,7 @@
shmem_swp_unmap(entry);
unlock:
spin_unlock(&info->lock);
- swap_free(swap);
+ swapcache_free(swap, NULL);
redirty:
set_page_dirty(page);
if (wbc->for_reclaim)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 1416e7e..19bdf30 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -162,11 +162,11 @@
return 1;
case -EEXIST:
/* Raced with "speculative" read_swap_cache_async */
- swap_free(entry);
+ swapcache_free(entry, NULL);
continue;
default:
/* -ENOMEM radix-tree allocation failure */
- swap_free(entry);
+ swapcache_free(entry, NULL);
return 0;
}
}
@@ -188,8 +188,7 @@
__delete_from_swap_cache(page);
spin_unlock_irq(&swapper_space.tree_lock);
- mem_cgroup_uncharge_swapcache(page, entry);
- swap_free(entry);
+ swapcache_free(entry, page);
page_cache_release(page);
}
@@ -293,7 +292,7 @@
/*
* Swap entry may have been freed since our caller observed it.
*/
- if (!swap_duplicate(entry))
+ if (!swapcache_prepare(entry))
break;
/*
@@ -317,7 +316,7 @@
}
ClearPageSwapBacked(new_page);
__clear_page_locked(new_page);
- swap_free(entry);
+ swapcache_free(entry, NULL);
} while (err != -ENOMEM);
if (new_page)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 312fafe..3187079 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -510,6 +510,16 @@
}
/*
+ * Called after dropping swapcache to decrease refcnt to swap entries.
+ */
+void swapcache_free(swp_entry_t entry, struct page *page)
+{
+ if (page)
+ mem_cgroup_uncharge_swapcache(page, entry);
+ return swap_free(entry);
+}
+
+/*
* How many references to page are currently swapped out?
*/
static inline int page_swapcount(struct page *page)
@@ -1979,6 +1989,15 @@
goto out;
}
+/*
+ * Called when allocating swap cache for exising swap entry,
+ */
+int swapcache_prepare(swp_entry_t entry)
+{
+ return swap_duplicate(entry);
+}
+
+
struct swap_info_struct *
get_swap_info_struct(unsigned type)
{
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2c4b945..52339dd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -470,8 +470,7 @@
swp_entry_t swap = { .val = page_private(page) };
__delete_from_swap_cache(page);
spin_unlock_irq(&mapping->tree_lock);
- mem_cgroup_uncharge_swapcache(page, swap);
- swap_free(swap);
+ swapcache_free(swap, page);
} else {
__remove_from_page_cache(page);
spin_unlock_irq(&mapping->tree_lock);