As ways to determine whether to allow certain functions to be
called.
This makes it easier to understand the code - the three functions
that can be called by the filesystem irregardless whether a backend is set or
not cleancache_init_fs, cleancache_init_shared_fs, and cleancache_invalidate_fs.
The rest of the cleancache functions end up being NOPs when the backend
has not yet registered.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
include/linux/cleancache.h | 16 +++++++++-----
include/linux/frontswap.h | 2 +-
mm/cleancache.c | 53 +++++++++++++++-------------------------------
3 files changed, 29 insertions(+), 42 deletions(-)
diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
index dfa1ccb..09df0e4 100644
--- a/include/linux/cleancache.h
+++ b/include/linux/cleancache.h
@@ -42,9 +42,15 @@ extern void __cleancache_put_page(struct page *);
extern void __cleancache_invalidate_page(struct address_space *, struct page *);
extern void __cleancache_invalidate_inode(struct address_space *);
extern void __cleancache_invalidate_fs(struct super_block *);
-extern int cleancache_enabled;
#ifdef CONFIG_CLEANCACHE
+#include <linux/jump_label.h>
+extern struct static_key cleancache_key;
+
+static inline bool cleancache_enabled(void)
+{
+ return static_key_false(&cleancache_key);
+}
static inline bool cleancache_fs_enabled(struct page *page)
{
return page->mapping->host->i_sb->cleancache_poolid >= 0;
@@ -86,14 +92,14 @@ static inline int cleancache_get_page(struct page *page)
{
int ret = -1;
- if (cleancache_enabled && cleancache_fs_enabled(page))
+ if (cleancache_enabled() && cleancache_fs_enabled(page))
ret = __cleancache_get_page(page);
return ret;
}
static inline void cleancache_put_page(struct page *page)
{
- if (cleancache_enabled && cleancache_fs_enabled(page))
+ if (cleancache_enabled() && cleancache_fs_enabled(page))
__cleancache_put_page(page);
}
@@ -101,13 +107,13 @@ static inline void cleancache_invalidate_page(struct address_space *mapping,
struct page *page)
{
/* careful... page->mapping is NULL sometimes when this is called */
- if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
+ if (cleancache_enabled() && cleancache_fs_enabled_mapping(mapping))
__cleancache_invalidate_page(mapping, page);
}
static inline void cleancache_invalidate_inode(struct address_space *mapping)
{
- if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
+ if (cleancache_enabled() && cleancache_fs_enabled_mapping(mapping))
__cleancache_invalidate_inode(mapping);
}
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index c120b90..3d72f14 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -113,7 +113,7 @@ static inline int frontswap_load(struct page *page)
static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
- if (frontswap_enabled)
+ if (static_key_false(&frontswap_key))
__frontswap_invalidate_page(type, offset);
}
diff --git a/mm/cleancache.c b/mm/cleancache.c
index 5d8dbb9..de0b905 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -24,9 +24,17 @@
* is not claimed (e.g. cleancache is config'ed on but remains
* disabled), so is preferred to the slower alternative: a function
* call that checks a non-global.
+ *
+ * When set to false (default) all calls to the cleancache functions, except
+ * the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
+ * by the if (cleancache_enabled()) return. This means multiple threads (from
+ * different filesystems) will be doing a NOP - b/c by default the
+ * cleancache_enabled() is returing false. The usage of a static_key allows
+ * us to patch up the code and allow the flood-gates to open when a backend
+ * has registered. Vice versa when unloading a backend.
*/
-int cleancache_enabled __read_mostly;
-EXPORT_SYMBOL(cleancache_enabled);
+struct static_key cleancache_key __read_mostly;
+EXPORT_SYMBOL(cleancache_key);
/*
* cleancache_ops is set by cleancache_ops_register to contain the pointers
@@ -70,18 +78,6 @@ static char *uuids[MAX_INITIALIZABLE_FS];
*/
static DEFINE_MUTEX(poolid_mutex);
/*
- * When set to false (default) all calls to the cleancache functions, except
- * the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
- * by the if (!cleancache_ops) return. This means multiple threads (from
- * different filesystems) will be checking cleancache_ops. The usage of a
- * bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are
- * OK if the time between the backend's have been initialized (and
- * cleancache_ops has been set to not NULL) and when the filesystems start
- * actually calling the backends. The inverse (when unloading) is obviously
- * not good - but this shim does not do that (yet).
- */
-
-/*
* The backends and filesystems work all asynchronously. This is b/c the
* backends can be built as modules.
* The usual sequence of events is:
@@ -89,13 +85,13 @@ static DEFINE_MUTEX(poolid_mutex);
* [shared_|]fs_poolid_map and uuids for.
*
* b). user does I/Os -> we call the rest of __cleancache_* functions
- * which return immediately as cleancache_ops is NULL.
+ * which return immediately as cleancache_enabled() returns false.
*
* c). modprobe zcache -> cleancache_register_ops. We init the backend
* and set cleancache_ops to the backend, and for any fs_poolid_map
* (which is set by __cleancache_init_fs) we initialize the poolid.
*
- * d). user does I/Os -> now that clean_ops is not NULL all the
+ * d). user does I/Os -> now that cleancache_enabled is turned to on, the
* __cleancache_* functions can call the backend. They all check
* that fs_poolid_map is valid and if so invoke the backend.
*
@@ -111,8 +107,8 @@ static DEFINE_MUTEX(poolid_mutex);
* of unmounting process).
*
* Note: The acute reader will notice that there is no "rmmod zcache" case.
- * This is b/c the functionality for that is not yet implemented and when
- * done, will require some extra locking not yet devised.
+ * This is b/c the functionality for that is not yet implemented in the
+ * backend. In here, it will require turning the cleancache_key off.
*/
/*
@@ -139,6 +135,8 @@ struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops)
*/
barrier();
cleancache_ops = ops;
+ if (!static_key_enabled(&cleancache_key))
+ static_key_slow_inc(&cleancache_key);
mutex_unlock(&poolid_mutex);
return old;
}
@@ -242,11 +240,6 @@ int __cleancache_get_page(struct page *page)
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!cleancache_ops) {
- cleancache_failed_gets++;
- goto out;
- }
-
VM_BUG_ON(!PageLocked(page));
fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
if (fake_pool_id < 0)
@@ -284,11 +277,6 @@ void __cleancache_put_page(struct page *page)
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!cleancache_ops) {
- cleancache_puts++;
- return;
- }
-
VM_BUG_ON(!PageLocked(page));
fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
if (fake_pool_id < 0)
@@ -320,9 +308,6 @@ void __cleancache_invalidate_page(struct address_space *mapping,
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!cleancache_ops)
- return;
-
if (fake_pool_id >= 0) {
pool_id = get_poolid_from_fake(fake_pool_id);
if (pool_id < 0)
@@ -353,9 +338,6 @@ void __cleancache_invalidate_inode(struct address_space *mapping)
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!cleancache_ops)
- return;
-
if (fake_pool_id < 0)
return;
@@ -389,7 +371,7 @@ void __cleancache_invalidate_fs(struct super_block *sb)
fs_poolid_map[index] = FS_UNKNOWN;
}
sb->cleancache_poolid = -1;
- if (cleancache_ops)
+ if (cleancache_enabled())
cleancache_ops->invalidate_fs(old_poolid);
mutex_unlock(&poolid_mutex);
}
@@ -414,7 +396,6 @@ static int __init init_cleancache(void)
fs_poolid_map[i] = FS_UNKNOWN;
shared_fs_poolid_map[i] = FS_UNKNOWN;
}
- cleancache_enabled = 1;
return 0;
}
module_init(init_cleancache)
--
1.8.0.2
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