[PATCH 12/13] frontswap: remove support for multiple ops
From: Christoph Hellwig
Date: Fri Dec 24 2021 - 01:23:50 EST
There is only a single instance of frontswap ops in the kernel, so
simplify the frontswap code by removing support for multiple operations.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/frontswap.h | 3 +--
mm/frontswap.c | 50 ++++++++++-----------------------------
mm/zswap.c | 8 +++++--
3 files changed, 19 insertions(+), 42 deletions(-)
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index c5b2848d22404..a631bac12220c 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -13,10 +13,9 @@ struct frontswap_ops {
int (*load)(unsigned, pgoff_t, struct page *); /* load a page */
void (*invalidate_page)(unsigned, pgoff_t); /* page no longer needed */
void (*invalidate_area)(unsigned); /* swap type just swapoff'ed */
- struct frontswap_ops *next; /* private pointer to next ops */
};
-extern void frontswap_register_ops(struct frontswap_ops *ops);
+int frontswap_register_ops(const struct frontswap_ops *ops);
extern void frontswap_init(unsigned type, unsigned long *map);
extern int __frontswap_store(struct page *page);
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 35040fa4eba83..6f69b044a8cc7 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -27,10 +27,7 @@ DEFINE_STATIC_KEY_FALSE(frontswap_enabled_key);
* may be registered, but implementations can never deregister. This
* is a simple singly-linked list of all registered implementations.
*/
-static struct frontswap_ops *frontswap_ops __read_mostly;
-
-#define for_each_frontswap_ops(ops) \
- for ((ops) = frontswap_ops; (ops); (ops) = (ops)->next)
+static const struct frontswap_ops *frontswap_ops __read_mostly;
#ifdef CONFIG_DEBUG_FS
/*
@@ -97,18 +94,14 @@ static inline void inc_frontswap_invalidates(void) { }
/*
* Register operations for frontswap
*/
-void frontswap_register_ops(struct frontswap_ops *ops)
+int frontswap_register_ops(const struct frontswap_ops *ops)
{
- /*
- * Setting frontswap_ops must happen after the ops->init() calls
- * above; cmpxchg implies smp_mb() which will ensure the init is
- * complete at this point.
- */
- do {
- ops->next = frontswap_ops;
- } while (cmpxchg(&frontswap_ops, ops->next, ops) != ops->next);
+ if (frontswap_ops)
+ return -EINVAL;
+ frontswap_ops = ops;
static_branch_inc(&frontswap_enabled_key);
+ return 0;
}
/*
@@ -117,7 +110,6 @@ void frontswap_register_ops(struct frontswap_ops *ops)
void frontswap_init(unsigned type, unsigned long *map)
{
struct swap_info_struct *sis = swap_info[type];
- struct frontswap_ops *ops;
VM_BUG_ON(sis == NULL);
@@ -133,9 +125,7 @@ void frontswap_init(unsigned type, unsigned long *map)
* p->frontswap set to something valid to work properly.
*/
frontswap_map_set(sis, map);
-
- for_each_frontswap_ops(ops)
- ops->init(type);
+ frontswap_ops->init(type);
}
static bool __frontswap_test(struct swap_info_struct *sis,
@@ -174,7 +164,6 @@ int __frontswap_store(struct page *page)
int type = swp_type(entry);
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- struct frontswap_ops *ops;
VM_BUG_ON(!frontswap_ops);
VM_BUG_ON(!PageLocked(page));
@@ -188,16 +177,10 @@ int __frontswap_store(struct page *page)
*/
if (__frontswap_test(sis, offset)) {
__frontswap_clear(sis, offset);
- for_each_frontswap_ops(ops)
- ops->invalidate_page(type, offset);
+ frontswap_ops->invalidate_page(type, offset);
}
- /* Try to store in each implementation, until one succeeds. */
- for_each_frontswap_ops(ops) {
- ret = ops->store(type, offset, page);
- if (!ret) /* successful store */
- break;
- }
+ ret = frontswap_ops->store(type, offset, page);
if (ret == 0) {
__frontswap_set(sis, offset);
inc_frontswap_succ_stores();
@@ -220,7 +203,6 @@ int __frontswap_load(struct page *page)
int type = swp_type(entry);
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- struct frontswap_ops *ops;
VM_BUG_ON(!frontswap_ops);
VM_BUG_ON(!PageLocked(page));
@@ -230,11 +212,7 @@ int __frontswap_load(struct page *page)
return -1;
/* Try loading from each implementation, until one succeeds. */
- for_each_frontswap_ops(ops) {
- ret = ops->load(type, offset, page);
- if (!ret) /* successful load */
- break;
- }
+ ret = frontswap_ops->load(type, offset, page);
if (ret == 0)
inc_frontswap_loads();
return ret;
@@ -247,7 +225,6 @@ int __frontswap_load(struct page *page)
void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
struct swap_info_struct *sis = swap_info[type];
- struct frontswap_ops *ops;
VM_BUG_ON(!frontswap_ops);
VM_BUG_ON(sis == NULL);
@@ -255,8 +232,7 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
if (!__frontswap_test(sis, offset))
return;
- for_each_frontswap_ops(ops)
- ops->invalidate_page(type, offset);
+ frontswap_ops->invalidate_page(type, offset);
__frontswap_clear(sis, offset);
inc_frontswap_invalidates();
}
@@ -268,7 +244,6 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
void __frontswap_invalidate_area(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- struct frontswap_ops *ops;
VM_BUG_ON(!frontswap_ops);
VM_BUG_ON(sis == NULL);
@@ -276,8 +251,7 @@ void __frontswap_invalidate_area(unsigned type)
if (sis->frontswap_map == NULL)
return;
- for_each_frontswap_ops(ops)
- ops->invalidate_area(type);
+ frontswap_ops->invalidate_area(type);
atomic_set(&sis->frontswap_pages, 0);
bitmap_zero(sis->frontswap_map, sis->max);
}
diff --git a/mm/zswap.c b/mm/zswap.c
index 7944e3e57e781..cdf6950fcb2e3 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1378,7 +1378,7 @@ static void zswap_frontswap_init(unsigned type)
zswap_trees[type] = tree;
}
-static struct frontswap_ops zswap_frontswap_ops = {
+static const struct frontswap_ops zswap_frontswap_ops = {
.store = zswap_frontswap_store,
.load = zswap_frontswap_load,
.invalidate_page = zswap_frontswap_invalidate_page,
@@ -1475,11 +1475,15 @@ static int __init init_zswap(void)
if (!shrink_wq)
goto fallback_fail;
- frontswap_register_ops(&zswap_frontswap_ops);
+ ret = frontswap_register_ops(&zswap_frontswap_ops);
+ if (ret)
+ goto destroy_wq;
if (zswap_debugfs_init())
pr_warn("debugfs initialization failed\n");
return 0;
+destroy_wq:
+ destroy_workqueue(shrink_wq);
fallback_fail:
if (pool)
zswap_pool_destroy(pool);
--
2.30.2