* [PATCH 01/11] mm: frontswap: lazy initialization to allow tmem backends to build/run as modules
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 02/11] frontswap: Make frontswap_init use a pointer for the ops Konrad Rzeszutek Wilk
` (9 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Stefan Hengelein, Florian Schmaus,
Andor Daam, Konrad Rzeszutek Wilk
From: Dan Magenheimer <dan.magenheimer@oracle.com>
With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to be
built/loaded as modules rather than built-in and enabled by a boot parameter,
this patch provides "lazy initialization", allowing backends to register to
frontswap even after swapon was run. Before a backend registers all calls
to init are recorded and the creation of tmem_pools delayed until a backend
registers or until a frontswap store is attempted.
Signed-off-by: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Florian Schmaus <fschmaus@gmail.com>
Signed-off-by: Andor Daam <andor.daam@googlemail.com>
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
[v1: Fixes per Seth Jennings suggestions]
[v2: Removed FRONTSWAP_HAS_.. ]
[v3: Fix up per Bob Liu <lliubbo@gmail.com> recommendations]
[v4: Fix up per Andrew's comments]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
mm/frontswap.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 85 insertions(+), 10 deletions(-)
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 2890e67..c05a9db 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -80,6 +80,46 @@ static inline void inc_frontswap_succ_stores(void) { }
static inline void inc_frontswap_failed_stores(void) { }
static inline void inc_frontswap_invalidates(void) { }
#endif
+
+/*
+ * Due to the asynchronous nature of the backends loading potentially
+ * _after_ the swap system has been activated, we have chokepoints
+ * on all frontswap functions to not call the backend until the backend
+ * has registered.
+ *
+ * Specifically when no backend is registered (nobody called
+ * frontswap_register_ops) all calls to frontswap_init (which is done via
+ * swapon -> enable_swap_info -> frontswap_init) are registered and remembered
+ * (via the setting of need_init bitmap) but fail to create tmem_pools. When a
+ * backend registers with frontswap at some later point the previous
+ * calls to frontswap_init are executed (by iterating over the need_init
+ * bitmap) to create tmem_pools and set the respective poolids. All of that is
+ * guarded by us using atomic bit operations on the 'need_init' bitmap.
+ *
+ * This would not guards us against the user deciding to call swapoff right as
+ * we are calling the backend to initialize (so swapon is in action).
+ * Fortunatly for us, the swapon_mutex has been taked by the callee so we are
+ * OK. The other scenario where calls to frontswap_store (called via
+ * swap_writepage) is racing with frontswap_invalidate_area (called via
+ * swapoff) is again guarded by the swap subsystem.
+ *
+ * While no backend is registered all calls to frontswap_[store|load|
+ * invalidate_area|invalidate_page] are ignored or fail.
+ *
+ * The time between the backend being registered and the swap file system
+ * calling the backend (via the frontswap_* functions) is indeterminate as
+ * backend_registered is not atomic_t (or a value guarded by a spinlock).
+ * That is OK as we are comfortable missing some of these calls to the newly
+ * registered backend.
+ *
+ * Obviously the opposite (unloading the backend) must be done after all
+ * the frontswap_[store|load|invalidate_area|invalidate_page] start
+ * ignorning or failing the requests - at which point backend_registered
+ * would have to be made in some fashion atomic.
+ */
+static DECLARE_BITMAP(need_init, MAX_SWAPFILES);
+static bool backend_registered __read_mostly;
+
/*
* Register operations for frontswap, returning previous thus allowing
* detection of multiple backends and possible nesting.
@@ -87,9 +127,22 @@ static inline void inc_frontswap_invalidates(void) { }
struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
{
struct frontswap_ops old = frontswap_ops;
+ int i;
frontswap_ops = *ops;
frontswap_enabled = true;
+
+ for (i = 0; i < MAX_SWAPFILES; i++) {
+ if (test_and_clear_bit(i, need_init))
+ (*frontswap_ops.init)(i);
+ }
+ /*
+ * We MUST have backend_registered set _after_ the frontswap_init's
+ * have been called. Otherwise __frontswap_store might fail. Hence
+ * the barrier to make sure compiler does not re-order us.
+ */
+ barrier();
+ backend_registered = true;
return old;
}
EXPORT_SYMBOL(frontswap_register_ops);
@@ -119,10 +172,17 @@ void __frontswap_init(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- BUG_ON(sis == NULL);
- if (sis->frontswap_map == NULL)
- return;
- frontswap_ops.init(type);
+ if (backend_registered) {
+ BUG_ON(sis == NULL);
+ if (sis->frontswap_map == NULL)
+ return;
+ (*frontswap_ops.init)(type);
+ }
+ else {
+ BUG_ON(type > MAX_SWAPFILES);
+ set_bit(type, need_init);
+ }
+
}
EXPORT_SYMBOL(__frontswap_init);
@@ -147,6 +207,11 @@ int __frontswap_store(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
+ if (!backend_registered) {
+ inc_frontswap_failed_stores();
+ return ret;
+ }
+
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
@@ -186,6 +251,9 @@ int __frontswap_load(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
+ if (!backend_registered)
+ return ret;
+
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
@@ -209,6 +277,9 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
struct swap_info_struct *sis = swap_info[type];
+ if (!backend_registered)
+ return;
+
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset)) {
frontswap_ops.invalidate_page(type, offset);
@@ -226,12 +297,15 @@ void __frontswap_invalidate_area(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- BUG_ON(sis == NULL);
- if (sis->frontswap_map == NULL)
- return;
- frontswap_ops.invalidate_area(type);
- atomic_set(&sis->frontswap_pages, 0);
- memset(sis->frontswap_map, 0, sis->max / sizeof(long));
+ if (backend_registered) {
+ BUG_ON(sis == NULL);
+ if (sis->frontswap_map == NULL)
+ return;
+ (*frontswap_ops.invalidate_area)(type);
+ atomic_set(&sis->frontswap_pages, 0);
+ memset(sis->frontswap_map, 0, sis->max / sizeof(long));
+ }
+ clear_bit(type, need_init);
}
EXPORT_SYMBOL(__frontswap_invalidate_area);
@@ -364,6 +438,7 @@ static int __init init_frontswap(void)
debugfs_create_u64("invalidates", S_IRUGO,
root, &frontswap_invalidates);
#endif
+ frontswap_enabled = 1;
return 0;
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 02/11] frontswap: Make frontswap_init use a pointer for the ops.
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 01/11] mm: frontswap: lazy initialization to allow tmem backends to build/run as modules Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 03/11] frontswap: Remove the check for frontswap_enabled Konrad Rzeszutek Wilk
` (8 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
This simplifies the code in the frontswap - we can get rid
of the 'backend_registered' test and instead check against
frontswap_ops.
[v1: Rebase on top of 703ba7fe5e085f2c85eeb451c2ac13cf275c7cb2
(ramster->zcache move]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/staging/zcache/zcache-main.c | 8 ++++----
drivers/xen/tmem.c | 6 +++---
include/linux/frontswap.h | 2 +-
mm/frontswap.c | 38 +++++++++++++++++-------------------
4 files changed, 26 insertions(+), 28 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 328898e..3365f59 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1825,9 +1825,9 @@ static struct frontswap_ops zcache_frontswap_ops = {
.init = zcache_frontswap_init
};
-struct frontswap_ops zcache_frontswap_register_ops(void)
+struct frontswap_ops *zcache_frontswap_register_ops(void)
{
- struct frontswap_ops old_ops =
+ struct frontswap_ops *old_ops =
frontswap_register_ops(&zcache_frontswap_ops);
return old_ops;
@@ -1994,7 +1994,7 @@ static int __init zcache_init(void)
pr_warn("%s: cleancache_ops overridden\n", namestr);
}
if (zcache_enabled && !disable_frontswap) {
- struct frontswap_ops old_ops;
+ struct frontswap_ops *old_ops;
old_ops = zcache_frontswap_register_ops();
if (frontswap_has_exclusive_gets)
@@ -2006,7 +2006,7 @@ static int __init zcache_init(void)
namestr, frontswap_has_exclusive_gets,
!disable_frontswap_ignore_nonactive);
#endif
- if (old_ops.init != NULL)
+ if (old_ops != NULL)
pr_warn("%s: frontswap_ops overridden\n", namestr);
}
if (ramster_enabled)
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 144564e..4b02c07 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -362,7 +362,7 @@ static int __init no_frontswap(char *s)
}
__setup("nofrontswap", no_frontswap);
-static struct frontswap_ops __initdata tmem_frontswap_ops = {
+static struct frontswap_ops tmem_frontswap_ops = {
.store = tmem_frontswap_store,
.load = tmem_frontswap_load,
.invalidate_page = tmem_frontswap_flush_page,
@@ -378,11 +378,11 @@ static int __init xen_tmem_init(void)
#ifdef CONFIG_FRONTSWAP
if (tmem_enabled && use_frontswap) {
char *s = "";
- struct frontswap_ops old_ops =
+ struct frontswap_ops *old_ops =
frontswap_register_ops(&tmem_frontswap_ops);
tmem_frontswap_poolid = -1;
- if (old_ops.init != NULL)
+ if (old_ops)
s = " (WARNING: frontswap_ops overridden)";
printk(KERN_INFO "frontswap enabled, RAM provided by "
"Xen Transcendent Memory\n");
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 3044254..d4f2987 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -14,7 +14,7 @@ struct frontswap_ops {
};
extern bool frontswap_enabled;
-extern struct frontswap_ops
+extern struct frontswap_ops *
frontswap_register_ops(struct frontswap_ops *ops);
extern void frontswap_shrink(unsigned long);
extern unsigned long frontswap_curr_pages(void);
diff --git a/mm/frontswap.c b/mm/frontswap.c
index c05a9db..b9b23b1 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -24,7 +24,7 @@
* frontswap_ops is set by frontswap_register_ops to contain the pointers
* to the frontswap "backend" implementation functions.
*/
-static struct frontswap_ops frontswap_ops __read_mostly;
+static struct frontswap_ops *frontswap_ops __read_mostly;
/*
* This global enablement flag reduces overhead on systems where frontswap_ops
@@ -108,41 +108,39 @@ static inline void inc_frontswap_invalidates(void) { }
*
* The time between the backend being registered and the swap file system
* calling the backend (via the frontswap_* functions) is indeterminate as
- * backend_registered is not atomic_t (or a value guarded by a spinlock).
+ * frontswap_ops is not atomic_t (or a value guarded by a spinlock).
* That is OK as we are comfortable missing some of these calls to the newly
* registered backend.
*
* Obviously the opposite (unloading the backend) must be done after all
* the frontswap_[store|load|invalidate_area|invalidate_page] start
- * ignorning or failing the requests - at which point backend_registered
+ * ignorning or failing the requests - at which point frontswap_ops
* would have to be made in some fashion atomic.
*/
static DECLARE_BITMAP(need_init, MAX_SWAPFILES);
-static bool backend_registered __read_mostly;
/*
* Register operations for frontswap, returning previous thus allowing
* detection of multiple backends and possible nesting.
*/
-struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
+struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
{
- struct frontswap_ops old = frontswap_ops;
+ struct frontswap_ops *old = frontswap_ops;
int i;
- frontswap_ops = *ops;
frontswap_enabled = true;
for (i = 0; i < MAX_SWAPFILES; i++) {
if (test_and_clear_bit(i, need_init))
- (*frontswap_ops.init)(i);
+ ops->init(i);
}
/*
- * We MUST have backend_registered set _after_ the frontswap_init's
+ * We MUST have frontswap_ops set _after_ the frontswap_init's
* have been called. Otherwise __frontswap_store might fail. Hence
* the barrier to make sure compiler does not re-order us.
*/
barrier();
- backend_registered = true;
+ frontswap_ops = ops;
return old;
}
EXPORT_SYMBOL(frontswap_register_ops);
@@ -172,11 +170,11 @@ void __frontswap_init(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- if (backend_registered) {
+ if (frontswap_ops) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
- (*frontswap_ops.init)(type);
+ frontswap_ops->init(type);
}
else {
BUG_ON(type > MAX_SWAPFILES);
@@ -207,7 +205,7 @@ int __frontswap_store(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!backend_registered) {
+ if (!frontswap_ops) {
inc_frontswap_failed_stores();
return ret;
}
@@ -216,7 +214,7 @@ int __frontswap_store(struct page *page)
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
dup = 1;
- ret = frontswap_ops.store(type, offset, page);
+ ret = frontswap_ops->store(type, offset, page);
if (ret == 0) {
frontswap_set(sis, offset);
inc_frontswap_succ_stores();
@@ -251,13 +249,13 @@ int __frontswap_load(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!backend_registered)
+ if (!frontswap_ops)
return ret;
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
- ret = frontswap_ops.load(type, offset, page);
+ ret = frontswap_ops->load(type, offset, page);
if (ret == 0) {
inc_frontswap_loads();
if (frontswap_tmem_exclusive_gets_enabled) {
@@ -277,12 +275,12 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
struct swap_info_struct *sis = swap_info[type];
- if (!backend_registered)
+ if (!frontswap_ops)
return;
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset)) {
- frontswap_ops.invalidate_page(type, offset);
+ frontswap_ops->invalidate_page(type, offset);
__frontswap_clear(sis, offset);
inc_frontswap_invalidates();
}
@@ -297,11 +295,11 @@ void __frontswap_invalidate_area(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- if (backend_registered) {
+ if (frontswap_ops) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
- (*frontswap_ops.invalidate_area)(type);
+ frontswap_ops->invalidate_area(type);
atomic_set(&sis->frontswap_pages, 0);
memset(sis->frontswap_map, 0, sis->max / sizeof(long));
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 03/11] frontswap: Remove the check for frontswap_enabled.
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 01/11] mm: frontswap: lazy initialization to allow tmem backends to build/run as modules Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 02/11] frontswap: Make frontswap_init use a pointer for the ops Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 04/11] frontswap: Use static_key instead of frontswap_enabled and frontswap_ops Konrad Rzeszutek Wilk
` (7 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
With the support for loading of backends as modules (see for example:
"staging: zcache: enable zcache to be built/loaded as a module"), the
frontswap_enabled is always set to true ("mm: frontswap: lazy
initialization to allow tmem backends to build/run as modules").
The next patch "frontswap: Use static_key instead of frontswap_enabled and
frontswap_ops" is are going to convert the frontswap_enabled to be a bit more
selective and be on/off depending on whether the backend has registered - and
not whether the frontswap API is enabled.
The two functions: frontswap_init and frontswap_invalidate_area
can be called anytime - they queue up which of the swap devices are
active and can use the frontswap API - once the backend is loaded.
As such there is no need to check for 'frontswap_enabled' at all.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
include/linux/frontswap.h | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index d4f2987..140323b 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -116,14 +116,12 @@ static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset)
static inline void frontswap_invalidate_area(unsigned type)
{
- if (frontswap_enabled)
- __frontswap_invalidate_area(type);
+ __frontswap_invalidate_area(type);
}
static inline void frontswap_init(unsigned type)
{
- if (frontswap_enabled)
- __frontswap_init(type);
+ __frontswap_init(type);
}
#endif /* _LINUX_FRONTSWAP_H */
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 04/11] frontswap: Use static_key instead of frontswap_enabled and frontswap_ops
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (2 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 03/11] frontswap: Remove the check for frontswap_enabled Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 05/11] frontswap: Get rid of swap_lock dependency Konrad Rzeszutek Wilk
` (6 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
As ways to determine whether to allow certain functions to be called.
This makes it easier to understand the code - the two functions
that can be called irregardless whether a backend is set or not is
the frontswap_init and frontswap_invalidate_area. The rest of the
frontswap functions end up being NOPs if the backend has not yet
registered.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
include/linux/frontswap.h | 17 ++++++++------
mm/frontswap.c | 58 ++++++++++++++++++++---------------------------
2 files changed, 34 insertions(+), 41 deletions(-)
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 140323b..8d24167 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -12,8 +12,6 @@ struct frontswap_ops {
void (*invalidate_page)(unsigned, pgoff_t);
void (*invalidate_area)(unsigned);
};
-
-extern bool frontswap_enabled;
extern struct frontswap_ops *
frontswap_register_ops(struct frontswap_ops *ops);
extern void frontswap_shrink(unsigned long);
@@ -29,25 +27,30 @@ extern void __frontswap_invalidate_page(unsigned, pgoff_t);
extern void __frontswap_invalidate_area(unsigned);
#ifdef CONFIG_FRONTSWAP
+#include <linux/jump_label.h>
+
+extern struct static_key frontswap_key;
+
+#define frontswap_enabled (1)
static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
{
bool ret = false;
- if (frontswap_enabled && sis->frontswap_map)
+ if (static_key_false(&frontswap_key) && sis->frontswap_map)
ret = test_bit(offset, sis->frontswap_map);
return ret;
}
static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset)
{
- if (frontswap_enabled && sis->frontswap_map)
+ if (static_key_false(&frontswap_key) && sis->frontswap_map)
set_bit(offset, sis->frontswap_map);
}
static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
{
- if (frontswap_enabled && sis->frontswap_map)
+ if (static_key_false(&frontswap_key) && sis->frontswap_map)
clear_bit(offset, sis->frontswap_map);
}
@@ -94,7 +97,7 @@ static inline int frontswap_store(struct page *page)
{
int ret = -1;
- if (frontswap_enabled)
+ if (static_key_false(&frontswap_key))
ret = __frontswap_store(page);
return ret;
}
@@ -103,7 +106,7 @@ static inline int frontswap_load(struct page *page)
{
int ret = -1;
- if (frontswap_enabled)
+ if (static_key_false(&frontswap_key))
ret = __frontswap_load(page);
return ret;
}
diff --git a/mm/frontswap.c b/mm/frontswap.c
index b9b23b1..ebf4c18 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -27,13 +27,13 @@
static struct frontswap_ops *frontswap_ops __read_mostly;
/*
- * This global enablement flag reduces overhead on systems where frontswap_ops
- * has not been registered, so is preferred to the slower alternative: a
- * function call that checks a non-global.
+ * The key is enabled once a backend has registered itself. The key
+ * by default is set to false which means that all (except frontswap_init
+ * and frontswap_invalidate) calls are NOPs. Once the key is turned on
+ * all functions execute the __frontswap code.
*/
-bool frontswap_enabled __read_mostly;
-EXPORT_SYMBOL(frontswap_enabled);
-
+struct static_key frontswap_key = STATIC_KEY_INIT_FALSE;
+EXPORT_SYMBOL(frontswap_key);
/*
* If enabled, frontswap_store will return failure even on success. As
* a result, the swap subsystem will always write the page to swap, in
@@ -83,8 +83,8 @@ static inline void inc_frontswap_invalidates(void) { }
/*
* Due to the asynchronous nature of the backends loading potentially
- * _after_ the swap system has been activated, we have chokepoints
- * on all frontswap functions to not call the backend until the backend
+ * _after_ the swap system has been activated, we have a static key
+ * on all almost frontswap functions to not call the backend until the backend
* has registered.
*
* Specifically when no backend is registered (nobody called
@@ -104,21 +104,19 @@ static inline void inc_frontswap_invalidates(void) { }
* swapoff) is again guarded by the swap subsystem.
*
* While no backend is registered all calls to frontswap_[store|load|
- * invalidate_area|invalidate_page] are ignored or fail.
+ * invalidate_page] are never executed as the __frontswap_*
+ * macros are based on the key which is set to false
*
* The time between the backend being registered and the swap file system
- * calling the backend (via the frontswap_* functions) is indeterminate as
- * frontswap_ops is not atomic_t (or a value guarded by a spinlock).
- * That is OK as we are comfortable missing some of these calls to the newly
- * registered backend.
+ * calling the backend (via the frontswap_* functions) is instant as the
+ * static_key patches over the code in question.
*
- * Obviously the opposite (unloading the backend) must be done after all
- * the frontswap_[store|load|invalidate_area|invalidate_page] start
- * ignorning or failing the requests - at which point frontswap_ops
- * would have to be made in some fashion atomic.
+ * Obviously the opposite (unloading the backend) can be done after the
+ * the frontswap_[store|load|invalidate_page] have been turned off so there
+ * are no more requests to process. The backend has to flush out all its
+ * pages back to the swap system after that.
*/
static DECLARE_BITMAP(need_init, MAX_SWAPFILES);
-
/*
* Register operations for frontswap, returning previous thus allowing
* detection of multiple backends and possible nesting.
@@ -128,8 +126,6 @@ struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
struct frontswap_ops *old = frontswap_ops;
int i;
- frontswap_enabled = true;
-
for (i = 0; i < MAX_SWAPFILES; i++) {
if (test_and_clear_bit(i, need_init))
ops->init(i);
@@ -141,6 +137,8 @@ struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
*/
barrier();
frontswap_ops = ops;
+ if (!static_key_enabled(&frontswap_key))
+ static_key_slow_inc(&frontswap_key);
return old;
}
EXPORT_SYMBOL(frontswap_register_ops);
@@ -165,12 +163,14 @@ EXPORT_SYMBOL(frontswap_tmem_exclusive_gets);
/*
* Called when a swap device is swapon'd.
+ *
+ * Can be called without any backend driver is registered.
*/
void __frontswap_init(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- if (frontswap_ops) {
+ if (static_key_false(&frontswap_key)) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
@@ -205,11 +205,6 @@ int __frontswap_store(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!frontswap_ops) {
- inc_frontswap_failed_stores();
- return ret;
- }
-
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
@@ -249,9 +244,6 @@ int __frontswap_load(struct page *page)
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!frontswap_ops)
- return ret;
-
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
@@ -275,9 +267,6 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
struct swap_info_struct *sis = swap_info[type];
- if (!frontswap_ops)
- return;
-
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset)) {
frontswap_ops->invalidate_page(type, offset);
@@ -290,12 +279,14 @@ EXPORT_SYMBOL(__frontswap_invalidate_page);
/*
* Invalidate all data from frontswap associated with all offsets for the
* specified swaptype.
+ *
+ * Can be called without any backend driver registered.
*/
void __frontswap_invalidate_area(unsigned type)
{
struct swap_info_struct *sis = swap_info[type];
- if (frontswap_ops) {
+ if (static_key_false(&frontswap_key)) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
@@ -436,7 +427,6 @@ static int __init init_frontswap(void)
debugfs_create_u64("invalidates", S_IRUGO,
root, &frontswap_invalidates);
#endif
- frontswap_enabled = 1;
return 0;
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 05/11] frontswap: Get rid of swap_lock dependency
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (3 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 04/11] frontswap: Use static_key instead of frontswap_enabled and frontswap_ops Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 06/11] mm: cleancache: lazy initialization to allow tmem backends to build/run as modules Konrad Rzeszutek Wilk
` (5 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
From: Minchan Kim <minchan@kernel.org>
Frontswap initialization routine depends on swap_lock, which want
to be atomic about frontswap's first appearance.
IOW, frontswap is not present and will fail all calls OR frontswap is
fully functional but if new swap_info_struct isn't registered
by enable_swap_info, swap subsystem doesn't start I/O so there is no
race
between init procedure and page I/O working on frontswap.
So let's remove unnecessary swap_lock dependency.
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
[v1: Rebased on my branch, reworked to work with backends loading late]
[v2: Added a check for !map]
[v3: Made the invalidate path follow the init path]
[v4: Address comments by Wanpeng Li <liwanp@linux.vnet.ibm.com>]
Signed-off-by: Konrad Rzeszutek Wilk <konrad@darnok.org>
---
include/linux/frontswap.h | 6 +++---
mm/frontswap.c | 29 ++++++++++++++++++++++-------
mm/swapfile.c | 18 +++++++++---------
3 files changed, 34 insertions(+), 19 deletions(-)
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 8d24167..c120b90 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -20,7 +20,7 @@ extern void frontswap_writethrough(bool);
#define FRONTSWAP_HAS_EXCLUSIVE_GETS
extern void frontswap_tmem_exclusive_gets(bool);
-extern void __frontswap_init(unsigned type);
+extern void __frontswap_init(unsigned type, unsigned long *map);
extern int __frontswap_store(struct page *page);
extern int __frontswap_load(struct page *page);
extern void __frontswap_invalidate_page(unsigned, pgoff_t);
@@ -122,9 +122,9 @@ static inline void frontswap_invalidate_area(unsigned type)
__frontswap_invalidate_area(type);
}
-static inline void frontswap_init(unsigned type)
+static inline void frontswap_init(unsigned type, unsigned long *map)
{
- __frontswap_init(type);
+ __frontswap_init(type, map);
}
#endif /* _LINUX_FRONTSWAP_H */
diff --git a/mm/frontswap.c b/mm/frontswap.c
index ebf4c18..c84fc3b 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -127,8 +127,13 @@ struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
int i;
for (i = 0; i < MAX_SWAPFILES; i++) {
- if (test_and_clear_bit(i, need_init))
+ if (test_and_clear_bit(i, need_init)) {
+ struct swap_info_struct *sis = swap_info[i];
+ /* __frontswap_init _should_ have set it! */
+ if (!sis->frontswap_map)
+ return ERR_PTR(-EINVAL);
ops->init(i);
+ }
}
/*
* We MUST have frontswap_ops set _after_ the frontswap_init's
@@ -166,16 +171,26 @@ EXPORT_SYMBOL(frontswap_tmem_exclusive_gets);
*
* Can be called without any backend driver is registered.
*/
-void __frontswap_init(unsigned type)
+void __frontswap_init(unsigned type, unsigned long *map)
{
struct swap_info_struct *sis = swap_info[type];
- if (static_key_false(&frontswap_key)) {
- BUG_ON(sis == NULL);
- if (sis->frontswap_map == NULL)
- return;
+ BUG_ON(sis == NULL);
+
+ /*
+ * p->frontswap is a bitmap that we MUST have to figure out which page
+ * has gone in frontswap. Without it there is no point of continuing.
+ */
+ if (WARN_ON(!map))
+ return;
+ /*
+ * Irregardless of whether the frontswap backend has been loaded
+ * before this function or it will be later, we _MUST_ have the
+ * p->frontswap set to something valid to work properly.
+ */
+ frontswap_map_set(sis, map);
+ if (static_key_false(&frontswap_key))
frontswap_ops->init(type);
- }
else {
BUG_ON(type > MAX_SWAPFILES);
set_bit(type, need_init);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e97a0e5..086c287 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1444,8 +1444,7 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
}
static void _enable_swap_info(struct swap_info_struct *p, int prio,
- unsigned char *swap_map,
- unsigned long *frontswap_map)
+ unsigned char *swap_map)
{
int i, prev;
@@ -1454,11 +1453,9 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio,
else
p->prio = --least_priority;
p->swap_map = swap_map;
- frontswap_map_set(p, frontswap_map);
p->flags |= SWP_WRITEOK;
nr_swap_pages += p->pages;
total_swap_pages += p->pages;
-
/* insert swap space into swap_list: */
prev = -1;
for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
@@ -1477,16 +1474,16 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
unsigned char *swap_map,
unsigned long *frontswap_map)
{
+ frontswap_init(p->type, frontswap_map);
spin_lock(&swap_lock);
- _enable_swap_info(p, prio, swap_map, frontswap_map);
- frontswap_init(p->type);
+ _enable_swap_info(p, prio, swap_map);
spin_unlock(&swap_lock);
}
static void reinsert_swap_info(struct swap_info_struct *p)
{
spin_lock(&swap_lock);
- _enable_swap_info(p, p->prio, p->swap_map, frontswap_map_get(p));
+ _enable_swap_info(p, p->prio, p->swap_map);
spin_unlock(&swap_lock);
}
@@ -1494,6 +1491,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
{
struct swap_info_struct *p = NULL;
unsigned char *swap_map;
+ unsigned long *frontswap_map;
struct file *swap_file, *victim;
struct address_space *mapping;
struct inode *inode;
@@ -1588,11 +1586,13 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
swap_map = p->swap_map;
p->swap_map = NULL;
p->flags = 0;
- frontswap_invalidate_area(type);
+ frontswap_map = frontswap_map_get(p);
+ frontswap_map_set(p, NULL);
spin_unlock(&swap_lock);
+ frontswap_invalidate_area(type);
mutex_unlock(&swapon_mutex);
vfree(swap_map);
- vfree(frontswap_map_get(p));
+ vfree(frontswap_map);
/* Destroy swap account informatin */
swap_cgroup_swapoff(type);
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 06/11] mm: cleancache: lazy initialization to allow tmem backends to build/run as modules
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (4 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 05/11] frontswap: Get rid of swap_lock dependency Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 07/11] cleancache: Make cleancache_init use a pointer for the ops Konrad Rzeszutek Wilk
` (4 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Stefan Hengelein, Florian Schmaus,
Andor Daam, Konrad Rzeszutek Wilk
From: Dan Magenheimer <dan.magenheimer@oracle.com>
With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to be
built/loaded as modules rather than built-in and enabled by a boot parameter,
this patch provides "lazy initialization", allowing backends to register to
cleancache even after filesystems were mounted. Calls to init_fs and
init_shared_fs are remembered as fake poolids but no real tmem_pools created.
On backend registration the fake poolids are mapped to real poolids and
respective tmem_pools.
Signed-off-by: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Florian Schmaus <fschmaus@gmail.com>
Signed-off-by: Andor Daam <andor.daam@googlemail.com>
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
[v1: Minor fixes: used #define for some values and bools]
[v2: Removed CLEANCACHE_HAS_LAZY_INIT]
[v3: Added more comments, added a lock for [shared_|]fs_poolid_map]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
mm/cleancache.c | 240 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 219 insertions(+), 21 deletions(-)
diff --git a/mm/cleancache.c b/mm/cleancache.c
index 32e6f41..e4dc314 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -45,15 +45,99 @@ static u64 cleancache_puts;
static u64 cleancache_invalidates;
/*
- * register operations for cleancache, returning previous thus allowing
- * detection of multiple backends and possible nesting
+ * When no backend is registered all calls to init_fs and init_shared_fs
+ * are registered and fake poolids (FAKE_FS_POOLID_OFFSET or
+ * FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array
+ * [shared_|]fs_poolid_map) are given to the respective super block
+ * (sb->cleancache_poolid) and no tmem_pools are created. When a backend
+ * registers with cleancache the previous calls to init_fs and init_shared_fs
+ * are executed to create tmem_pools and set the respective poolids. While no
+ * backend is registered all "puts", "gets" and "flushes" are ignored or failed.
+ */
+#define MAX_INITIALIZABLE_FS 32
+#define FAKE_FS_POOLID_OFFSET 1000
+#define FAKE_SHARED_FS_POOLID_OFFSET 2000
+
+#define FS_NO_BACKEND (-1)
+#define FS_UNKNOWN (-2)
+static int fs_poolid_map[MAX_INITIALIZABLE_FS];
+static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS];
+static char *uuids[MAX_INITIALIZABLE_FS];
+/*
+ * Mutex for the [shared_|]fs_poolid_map to guard against multiple threads
+ * invoking umount (and ending in __cleancache_invalidate_fs) and also multiple
+ * threads calling mount (and ending up in __cleancache_init_[shared|]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 (!backend_registered) return. This means multiple threads (from
+ * different filesystems) will be checking backend_registered. 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
+ * backend_registered has been set to true) 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).
+ */
+static bool backend_registered __read_mostly;
+
+/*
+ * The backends and filesystems work all asynchronously. This is b/c the
+ * backends can be built as modules.
+ * The usual sequence of events is:
+ * a) mount / -> __cleancache_init_fs is called. We set the
+ * [shared_|]fs_poolid_map and uuids for.
+ *
+ * b). user does I/Os -> we call the rest of __cleancache_* functions
+ * which return immediately as backend_registered is false.
+ *
+ * c). modprobe zcache -> cleancache_register_ops. We init the backend
+ * and set backend_registered to true, and for any fs_poolid_map
+ * (which is set by __cleancache_init_fs) we initialize the poolid.
+ *
+ * d). user does I/Os -> now that backend_registered is true all the
+ * __cleancache_* functions can call the backend. They all check
+ * that fs_poolid_map is valid and if so invoke the backend.
+ *
+ * e). umount / -> __cleancache_invalidate_fs, the fs_poolid_map is
+ * reset (which is the second check in the __cleancache_* ops
+ * to call the backend).
+ *
+ * The sequence of event could also be c), followed by a), and d). and e). The
+ * c) would not happen anymore. There is also the chance of c), and one thread
+ * doing a) + d), and another doing e). For that case we depend on the
+ * filesystem calling __cleancache_invalidate_fs in the proper sequence (so
+ * that it handles all I/Os before it invalidates the fs (which is last part
+ * 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.
+ */
+
+/*
+ * Register operations for cleancache, returning previous thus allowing
+ * detection of multiple backends and possible nesting.
*/
struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
{
struct cleancache_ops old = cleancache_ops;
+ int i;
+ mutex_lock(&poolid_mutex);
cleancache_ops = *ops;
- cleancache_enabled = 1;
+
+ backend_registered = true;
+ for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+ if (fs_poolid_map[i] == FS_NO_BACKEND)
+ fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
+ if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
+ shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
+ (uuids[i], PAGE_SIZE);
+ }
+out:
+ mutex_unlock(&poolid_mutex);
return old;
}
EXPORT_SYMBOL(cleancache_register_ops);
@@ -61,15 +145,42 @@ EXPORT_SYMBOL(cleancache_register_ops);
/* Called by a cleancache-enabled filesystem at time of mount */
void __cleancache_init_fs(struct super_block *sb)
{
- sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
+ int i;
+
+ mutex_lock(&poolid_mutex);
+ for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+ if (fs_poolid_map[i] == FS_UNKNOWN) {
+ sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
+ if (backend_registered)
+ fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
+ else
+ fs_poolid_map[i] = FS_NO_BACKEND;
+ break;
+ }
+ }
+ mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_init_fs);
/* Called by a cleancache-enabled clustered filesystem at time of mount */
void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
{
- sb->cleancache_poolid =
- (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
+ int i;
+
+ mutex_lock(&poolid_mutex);
+ for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+ if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
+ sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
+ uuids[i] = uuid;
+ if (backend_registered)
+ shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
+ (uuid, PAGE_SIZE);
+ else
+ shared_fs_poolid_map[i] = FS_NO_BACKEND;
+ break;
+ }
+ }
+ mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_init_shared_fs);
@@ -99,27 +210,53 @@ static int cleancache_get_key(struct inode *inode,
}
/*
+ * Returns a pool_id that is associated with a given fake poolid.
+ */
+static int get_poolid_from_fake(int fake_pool_id)
+{
+ if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET)
+ return shared_fs_poolid_map[fake_pool_id -
+ FAKE_SHARED_FS_POOLID_OFFSET];
+ else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET)
+ return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET];
+ return FS_NO_BACKEND;
+}
+
+/*
* "Get" data from cleancache associated with the poolid/inode/index
* that were specified when the data was put to cleanache and, if
* successful, use it to fill the specified page with data and return 0.
* The pageframe is unchanged and returns -1 if the get fails.
* Page must be locked by caller.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
*/
int __cleancache_get_page(struct page *page)
{
int ret = -1;
int pool_id;
+ int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
+ if (!backend_registered) {
+ cleancache_failed_gets++;
+ goto out;
+ }
+
VM_BUG_ON(!PageLocked(page));
- pool_id = page->mapping->host->i_sb->cleancache_poolid;
- if (pool_id < 0)
+ fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
+ if (fake_pool_id < 0)
goto out;
+ pool_id = get_poolid_from_fake(fake_pool_id);
if (cleancache_get_key(page->mapping->host, &key) < 0)
goto out;
- ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
+ if (pool_id >= 0)
+ ret = (*cleancache_ops.get_page)(pool_id,
+ key, page->index, page);
if (ret == 0)
cleancache_succ_gets++;
else
@@ -134,16 +271,31 @@ EXPORT_SYMBOL(__cleancache_get_page);
* (previously-obtained per-filesystem) poolid and the page's,
* inode and page index. Page must be locked. Note that a put_page
* always "succeeds", though a subsequent get_page may succeed or fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
*/
void __cleancache_put_page(struct page *page)
{
int pool_id;
+ int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
+ if (!backend_registered) {
+ cleancache_puts++;
+ return;
+ }
+
VM_BUG_ON(!PageLocked(page));
- pool_id = page->mapping->host->i_sb->cleancache_poolid;
+ fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
+ if (fake_pool_id < 0)
+ return;
+
+ pool_id = get_poolid_from_fake(fake_pool_id);
+
if (pool_id >= 0 &&
- cleancache_get_key(page->mapping->host, &key) >= 0) {
+ cleancache_get_key(page->mapping->host, &key) >= 0) {
(*cleancache_ops.put_page)(pool_id, key, page->index, page);
cleancache_puts++;
}
@@ -153,19 +305,31 @@ EXPORT_SYMBOL(__cleancache_put_page);
/*
* Invalidate any data from cleancache associated with the poolid and the
* page's inode and page index so that a subsequent "get" will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
*/
void __cleancache_invalidate_page(struct address_space *mapping,
struct page *page)
{
/* careful... page->mapping is NULL sometimes when this is called */
- int pool_id = mapping->host->i_sb->cleancache_poolid;
+ int pool_id;
+ int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (pool_id >= 0) {
+ if (!backend_registered)
+ return;
+
+ if (fake_pool_id >= 0) {
+ pool_id = get_poolid_from_fake(fake_pool_id);
+ if (pool_id < 0)
+ return;
+
VM_BUG_ON(!PageLocked(page));
if (cleancache_get_key(mapping->host, &key) >= 0) {
(*cleancache_ops.invalidate_page)(pool_id,
- key, page->index);
+ key, page->index);
cleancache_invalidates++;
}
}
@@ -176,12 +340,25 @@ EXPORT_SYMBOL(__cleancache_invalidate_page);
* Invalidate all data from cleancache associated with the poolid and the
* mappings's inode so that all subsequent gets to this poolid/inode
* will fail.
+ *
+ * The function has two checks before any action is taken - whether
+ * a backend is registered and whether the sb->cleancache_poolid
+ * is correct.
*/
void __cleancache_invalidate_inode(struct address_space *mapping)
{
- int pool_id = mapping->host->i_sb->cleancache_poolid;
+ int pool_id;
+ int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
+ if (!backend_registered)
+ return;
+
+ if (fake_pool_id < 0)
+ return;
+
+ pool_id = get_poolid_from_fake(fake_pool_id);
+
if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
(*cleancache_ops.invalidate_inode)(pool_id, key);
}
@@ -189,21 +366,37 @@ EXPORT_SYMBOL(__cleancache_invalidate_inode);
/*
* Called by any cleancache-enabled filesystem at time of unmount;
- * note that pool_id is surrendered and may be reutrned by a subsequent
- * cleancache_init_fs or cleancache_init_shared_fs
+ * note that pool_id is surrendered and may be returned by a subsequent
+ * cleancache_init_fs or cleancache_init_shared_fs.
*/
void __cleancache_invalidate_fs(struct super_block *sb)
{
- if (sb->cleancache_poolid >= 0) {
- int old_poolid = sb->cleancache_poolid;
- sb->cleancache_poolid = -1;
- (*cleancache_ops.invalidate_fs)(old_poolid);
+ int index;
+ int fake_pool_id = sb->cleancache_poolid;
+ int old_poolid = fake_pool_id;
+
+ mutex_lock(&poolid_mutex);
+ if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) {
+ index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET;
+ old_poolid = shared_fs_poolid_map[index];
+ shared_fs_poolid_map[index] = FS_UNKNOWN;
+ uuids[index] = NULL;
+ } else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) {
+ index = fake_pool_id - FAKE_FS_POOLID_OFFSET;
+ old_poolid = fs_poolid_map[index];
+ fs_poolid_map[index] = FS_UNKNOWN;
}
+ sb->cleancache_poolid = -1;
+ if (backend_registered)
+ (*cleancache_ops.invalidate_fs)(old_poolid);
+ mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);
static int __init init_cleancache(void)
{
+ int i;
+
#ifdef CONFIG_DEBUG_FS
struct dentry *root = debugfs_create_dir("cleancache", NULL);
if (root == NULL)
@@ -215,6 +408,11 @@ static int __init init_cleancache(void)
debugfs_create_u64("invalidates", S_IRUGO,
root, &cleancache_invalidates);
#endif
+ for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
+ 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
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 07/11] cleancache: Make cleancache_init use a pointer for the ops
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (5 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 06/11] mm: cleancache: lazy initialization to allow tmem backends to build/run as modules Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 08/11] cleancache: Remove the check for cleancache_enabled Konrad Rzeszutek Wilk
` (3 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
Instead of using a backend_registered to determine whether
a backend is enabled. This allows us to remove the
backend_register check and just do 'if (cleancache_ops)'
[v1: Rebase on top of b97c4b430b0a405a57c78607b520d8000329e259
(ramster->zcache move]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/staging/zcache/zcache-main.c | 8 ++---
drivers/xen/tmem.c | 6 ++--
include/linux/cleancache.h | 2 +-
mm/cleancache.c | 62 +++++++++++++++++++-----------------
4 files changed, 40 insertions(+), 38 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 3365f59..3554987 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1694,9 +1694,9 @@ static struct cleancache_ops zcache_cleancache_ops = {
.init_fs = zcache_cleancache_init_fs
};
-struct cleancache_ops zcache_cleancache_register_ops(void)
+struct cleancache_ops *zcache_cleancache_register_ops(void)
{
- struct cleancache_ops old_ops =
+ struct cleancache_ops *old_ops =
cleancache_register_ops(&zcache_cleancache_ops);
return old_ops;
@@ -1980,7 +1980,7 @@ static int __init zcache_init(void)
}
zbud_init();
if (zcache_enabled && !disable_cleancache) {
- struct cleancache_ops old_ops;
+ struct cleancache_ops *old_ops;
register_shrinker(&zcache_shrinker);
old_ops = zcache_cleancache_register_ops();
@@ -1990,7 +1990,7 @@ static int __init zcache_init(void)
pr_info("%s: cleancache: ignorenonactive = %d\n",
namestr, !disable_cleancache_ignore_nonactive);
#endif
- if (old_ops.init_fs != NULL)
+ if (old_ops != NULL)
pr_warn("%s: cleancache_ops overridden\n", namestr);
}
if (zcache_enabled && !disable_frontswap) {
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 4b02c07..15e776c 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -236,7 +236,7 @@ static int __init no_cleancache(char *s)
}
__setup("nocleancache", no_cleancache);
-static struct cleancache_ops __initdata tmem_cleancache_ops = {
+static struct cleancache_ops tmem_cleancache_ops = {
.put_page = tmem_cleancache_put_page,
.get_page = tmem_cleancache_get_page,
.invalidate_page = tmem_cleancache_flush_page,
@@ -392,9 +392,9 @@ static int __init xen_tmem_init(void)
BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
if (tmem_enabled && use_cleancache) {
char *s = "";
- struct cleancache_ops old_ops =
+ struct cleancache_ops *old_ops =
cleancache_register_ops(&tmem_cleancache_ops);
- if (old_ops.init_fs != NULL)
+ if (old_ops)
s = " (WARNING: cleancache_ops overridden)";
printk(KERN_INFO "cleancache enabled, RAM provided by "
"Xen Transcendent Memory%s\n", s);
diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
index 42e55de..3af5ea8 100644
--- a/include/linux/cleancache.h
+++ b/include/linux/cleancache.h
@@ -33,7 +33,7 @@ struct cleancache_ops {
void (*invalidate_fs)(int);
};
-extern struct cleancache_ops
+extern struct cleancache_ops *
cleancache_register_ops(struct cleancache_ops *ops);
extern void __cleancache_init_fs(struct super_block *);
extern void __cleancache_init_shared_fs(char *, struct super_block *);
diff --git a/mm/cleancache.c b/mm/cleancache.c
index e4dc314..5d8dbb9 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -32,7 +32,7 @@ EXPORT_SYMBOL(cleancache_enabled);
* cleancache_ops is set by cleancache_ops_register to contain the pointers
* to the cleancache "backend" implementation functions.
*/
-static struct cleancache_ops cleancache_ops __read_mostly;
+static struct cleancache_ops *cleancache_ops __read_mostly;
/*
* Counters available via /sys/kernel/debug/frontswap (if debugfs is
@@ -72,15 +72,14 @@ 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 (!backend_registered) return. This means multiple threads (from
- * different filesystems) will be checking backend_registered. The usage of a
+ * 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
- * backend_registered has been set to true) and when the filesystems start
+ * 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).
*/
-static bool backend_registered __read_mostly;
/*
* The backends and filesystems work all asynchronously. This is b/c the
@@ -90,13 +89,13 @@ static bool backend_registered __read_mostly;
* [shared_|]fs_poolid_map and uuids for.
*
* b). user does I/Os -> we call the rest of __cleancache_* functions
- * which return immediately as backend_registered is false.
+ * which return immediately as cleancache_ops is NULL.
*
* c). modprobe zcache -> cleancache_register_ops. We init the backend
- * and set backend_registered to true, and for any fs_poolid_map
+ * 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 backend_registered is true all the
+ * d). user does I/Os -> now that clean_ops is not NULL all the
* __cleancache_* functions can call the backend. They all check
* that fs_poolid_map is valid and if so invoke the backend.
*
@@ -120,23 +119,26 @@ static bool backend_registered __read_mostly;
* Register operations for cleancache, returning previous thus allowing
* detection of multiple backends and possible nesting.
*/
-struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
+struct cleancache_ops *cleancache_register_ops(struct cleancache_ops *ops)
{
- struct cleancache_ops old = cleancache_ops;
+ struct cleancache_ops *old = cleancache_ops;
int i;
mutex_lock(&poolid_mutex);
- cleancache_ops = *ops;
-
- backend_registered = true;
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
if (fs_poolid_map[i] == FS_NO_BACKEND)
- fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
+ fs_poolid_map[i] = ops->init_fs(PAGE_SIZE);
if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
- shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
+ shared_fs_poolid_map[i] = ops->init_shared_fs
(uuids[i], PAGE_SIZE);
}
-out:
+ /*
+ * We MUST set cleancache_ops _after_ we have called the backends
+ * init_fs or init_shared_fs functions. Otherwise the compiler might
+ * re-order where cleancache_ops is set in this function.
+ */
+ barrier();
+ cleancache_ops = ops;
mutex_unlock(&poolid_mutex);
return old;
}
@@ -151,8 +153,8 @@ void __cleancache_init_fs(struct super_block *sb)
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
if (fs_poolid_map[i] == FS_UNKNOWN) {
sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
- if (backend_registered)
- fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
+ if (cleancache_ops)
+ fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE);
else
fs_poolid_map[i] = FS_NO_BACKEND;
break;
@@ -172,8 +174,8 @@ void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
uuids[i] = uuid;
- if (backend_registered)
- shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
+ if (cleancache_ops)
+ shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs
(uuid, PAGE_SIZE);
else
shared_fs_poolid_map[i] = FS_NO_BACKEND;
@@ -240,7 +242,7 @@ int __cleancache_get_page(struct page *page)
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered) {
+ if (!cleancache_ops) {
cleancache_failed_gets++;
goto out;
}
@@ -255,7 +257,7 @@ int __cleancache_get_page(struct page *page)
goto out;
if (pool_id >= 0)
- ret = (*cleancache_ops.get_page)(pool_id,
+ ret = cleancache_ops->get_page(pool_id,
key, page->index, page);
if (ret == 0)
cleancache_succ_gets++;
@@ -282,7 +284,7 @@ void __cleancache_put_page(struct page *page)
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered) {
+ if (!cleancache_ops) {
cleancache_puts++;
return;
}
@@ -296,7 +298,7 @@ void __cleancache_put_page(struct page *page)
if (pool_id >= 0 &&
cleancache_get_key(page->mapping->host, &key) >= 0) {
- (*cleancache_ops.put_page)(pool_id, key, page->index, page);
+ cleancache_ops->put_page(pool_id, key, page->index, page);
cleancache_puts++;
}
}
@@ -318,7 +320,7 @@ 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 (!backend_registered)
+ if (!cleancache_ops)
return;
if (fake_pool_id >= 0) {
@@ -328,7 +330,7 @@ void __cleancache_invalidate_page(struct address_space *mapping,
VM_BUG_ON(!PageLocked(page));
if (cleancache_get_key(mapping->host, &key) >= 0) {
- (*cleancache_ops.invalidate_page)(pool_id,
+ cleancache_ops->invalidate_page(pool_id,
key, page->index);
cleancache_invalidates++;
}
@@ -351,7 +353,7 @@ 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 (!backend_registered)
+ if (!cleancache_ops)
return;
if (fake_pool_id < 0)
@@ -360,7 +362,7 @@ void __cleancache_invalidate_inode(struct address_space *mapping)
pool_id = get_poolid_from_fake(fake_pool_id);
if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
- (*cleancache_ops.invalidate_inode)(pool_id, key);
+ cleancache_ops->invalidate_inode(pool_id, key);
}
EXPORT_SYMBOL(__cleancache_invalidate_inode);
@@ -387,8 +389,8 @@ void __cleancache_invalidate_fs(struct super_block *sb)
fs_poolid_map[index] = FS_UNKNOWN;
}
sb->cleancache_poolid = -1;
- if (backend_registered)
- (*cleancache_ops.invalidate_fs)(old_poolid);
+ if (cleancache_ops)
+ cleancache_ops->invalidate_fs(old_poolid);
mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 08/11] cleancache: Remove the check for cleancache_enabled.
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (6 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 07/11] cleancache: Make cleancache_init use a pointer for the ops Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 09/11] cleancache: Use static_key instead of cleancache_ops and cleancache_enabled Konrad Rzeszutek Wilk
` (2 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
With the support for loading of backends as modules, the
cleancache_enabled is always set to true. The next subsequent patches
are going to convert the cleancache_enabled to be a bit more selective
and be on/off depending on whether the backend has registered - and not
whether the cleancache API is enabled.
The three functions: cleancache_init_[shared|]fs and
cleancache_invalidate_fs can be called anytime - they queue up which
of the filesystems are active and can use the cleancache API - and when
the backend is registered they will know which filesystem to
process.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
include/linux/cleancache.h | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
index 3af5ea8..dfa1ccb 100644
--- a/include/linux/cleancache.h
+++ b/include/linux/cleancache.h
@@ -74,14 +74,12 @@ static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping)
static inline void cleancache_init_fs(struct super_block *sb)
{
- if (cleancache_enabled)
- __cleancache_init_fs(sb);
+ __cleancache_init_fs(sb);
}
static inline void cleancache_init_shared_fs(char *uuid, struct super_block *sb)
{
- if (cleancache_enabled)
- __cleancache_init_shared_fs(uuid, sb);
+ __cleancache_init_shared_fs(uuid, sb);
}
static inline int cleancache_get_page(struct page *page)
@@ -115,8 +113,7 @@ static inline void cleancache_invalidate_inode(struct address_space *mapping)
static inline void cleancache_invalidate_fs(struct super_block *sb)
{
- if (cleancache_enabled)
- __cleancache_invalidate_fs(sb);
+ __cleancache_invalidate_fs(sb);
}
#endif /* _LINUX_CLEANCACHE_H */
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 09/11] cleancache: Use static_key instead of cleancache_ops and cleancache_enabled.
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (7 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 08/11] cleancache: Remove the check for cleancache_enabled Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 10/11] xen: tmem: enable Xen tmem shim to be built/loaded as a module Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 11/11] zcache/tmem: Better error checking on frontswap_register_ops return value Konrad Rzeszutek Wilk
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
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@oracle.com>
---
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
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 10/11] xen: tmem: enable Xen tmem shim to be built/loaded as a module
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (8 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 09/11] cleancache: Use static_key instead of cleancache_ops and cleancache_enabled Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
2013-02-15 20:20 ` [PATCH 11/11] zcache/tmem: Better error checking on frontswap_register_ops return value Konrad Rzeszutek Wilk
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
From: Dan Magenheimer <dan.magenheimer@oracle.com>
Allow Xen tmem shim to be built/loaded as a module. Xen self-ballooning
and frontswap-selfshrinking are now also "lazily" initialized when the
Xen tmem shim is loaded as a module, unless explicitly disabled
by module parameters.
Note runtime dependency disallows loading if cleancache/frontswap lazy
initialization patches are not present.
If built-in (not built as a module), the original mechanism of enabling via
a kernel boot parameter is retained, but this should be considered deprecated.
Note that module unload is explicitly not yet supported.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
[v1: Removed the [CLEANCACHE|FRONTSWAP]_HAS_LAZY_INIT ifdef]
[v2: Squashed the xen/tmem: Remove the subsys call patch in]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/xen/Kconfig | 4 ++--
drivers/xen/tmem.c | 38 +++++++++++++++++++++++++++++---------
drivers/xen/xen-selfballoon.c | 13 +++++--------
include/xen/tmem.h | 8 ++++++++
4 files changed, 44 insertions(+), 19 deletions(-)
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index cabfa97..981646e 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -145,9 +145,9 @@ config SWIOTLB_XEN
select SWIOTLB
config XEN_TMEM
- bool
+ tristate
depends on !ARM
- default y if (CLEANCACHE || FRONTSWAP)
+ default m if (CLEANCACHE || FRONTSWAP)
help
Shim to interface in-kernel Transcendent Memory hooks
(e.g. cleancache and frontswap) to Xen tmem hypercalls.
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 15e776c..9a4a9ec 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -5,6 +5,7 @@
* Author: Dan Magenheimer
*/
+#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
@@ -128,6 +129,7 @@ static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
}
+#ifndef CONFIG_XEN_TMEM_MODULE
bool __read_mostly tmem_enabled = false;
static int __init enable_tmem(char *s)
@@ -136,6 +138,7 @@ static int __init enable_tmem(char *s)
return 1;
}
__setup("tmem", enable_tmem);
+#endif
#ifdef CONFIG_CLEANCACHE
static int xen_tmem_destroy_pool(u32 pool_id)
@@ -227,14 +230,19 @@ static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
}
-static bool __initdata use_cleancache = true;
-
+static bool disable_cleancache __read_mostly;
+static bool disable_selfballooning __read_mostly;
+#ifdef CONFIG_XEN_TMEM_MODULE
+module_param(disable_cleancache, bool, S_IRUGO);
+module_param(disable_selfballooning, bool, S_IRUGO);
+#else
static int __init no_cleancache(char *s)
{
- use_cleancache = false;
+ disable_cleancache = true;
return 1;
}
__setup("nocleancache", no_cleancache);
+#endif
static struct cleancache_ops tmem_cleancache_ops = {
.put_page = tmem_cleancache_put_page,
@@ -353,14 +361,19 @@ static void tmem_frontswap_init(unsigned ignored)
xen_tmem_new_pool(private, TMEM_POOL_PERSIST, PAGE_SIZE);
}
-static bool __initdata use_frontswap = true;
-
+static bool disable_frontswap __read_mostly;
+static bool disable_frontswap_selfshrinking __read_mostly;
+#ifdef CONFIG_XEN_TMEM_MODULE
+module_param(disable_frontswap, bool, S_IRUGO);
+module_param(disable_frontswap_selfshrinking, bool, S_IRUGO);
+#else
static int __init no_frontswap(char *s)
{
- use_frontswap = false;
+ disable_frontswap = true;
return 1;
}
__setup("nofrontswap", no_frontswap);
+#endif
static struct frontswap_ops tmem_frontswap_ops = {
.store = tmem_frontswap_store,
@@ -371,12 +384,12 @@ static struct frontswap_ops tmem_frontswap_ops = {
};
#endif
-static int __init xen_tmem_init(void)
+static int xen_tmem_init(void)
{
if (!xen_domain())
return 0;
#ifdef CONFIG_FRONTSWAP
- if (tmem_enabled && use_frontswap) {
+ if (tmem_enabled && !disable_frontswap) {
char *s = "";
struct frontswap_ops *old_ops =
frontswap_register_ops(&tmem_frontswap_ops);
@@ -390,7 +403,7 @@ static int __init xen_tmem_init(void)
#endif
#ifdef CONFIG_CLEANCACHE
BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
- if (tmem_enabled && use_cleancache) {
+ if (tmem_enabled && !disable_cleancache) {
char *s = "";
struct cleancache_ops *old_ops =
cleancache_register_ops(&tmem_cleancache_ops);
@@ -400,7 +413,14 @@ static int __init xen_tmem_init(void)
"Xen Transcendent Memory%s\n", s);
}
#endif
+#ifdef CONFIG_XEN_SELFBALLOONING
+ xen_selfballoon_init(!disable_selfballooning,
+ !disable_frontswap_selfshrinking);
+#endif
return 0;
}
module_init(xen_tmem_init)
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
+MODULE_DESCRIPTION("Shim to Xen transcendent memory");
diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 2552d3e..f2ef569 100644
--- a/drivers/xen/xen-selfballoon.c
+++ b/drivers/xen/xen-selfballoon.c
@@ -121,7 +121,7 @@ static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
static bool frontswap_selfshrinking __read_mostly;
/* Enable/disable with kernel boot option. */
-static bool use_frontswap_selfshrink __initdata = true;
+static bool use_frontswap_selfshrink = true;
/*
* The default values for the following parameters were deemed reasonable
@@ -185,7 +185,7 @@ static int __init xen_nofrontswap_selfshrink_setup(char *s)
__setup("noselfshrink", xen_nofrontswap_selfshrink_setup);
/* Disable with kernel boot option. */
-static bool use_selfballooning __initdata = true;
+static bool use_selfballooning = true;
static int __init xen_noselfballooning_setup(char *s)
{
@@ -196,7 +196,7 @@ static int __init xen_noselfballooning_setup(char *s)
__setup("noselfballooning", xen_noselfballooning_setup);
#else /* !CONFIG_FRONTSWAP */
/* Enable with kernel boot option. */
-static bool use_selfballooning __initdata = false;
+static bool use_selfballooning;
static int __init xen_selfballooning_setup(char *s)
{
@@ -537,7 +537,7 @@ int register_xen_selfballooning(struct device *dev)
}
EXPORT_SYMBOL(register_xen_selfballooning);
-static int __init xen_selfballoon_init(void)
+int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink)
{
bool enable = false;
@@ -571,7 +571,4 @@ static int __init xen_selfballoon_init(void)
return 0;
}
-
-subsys_initcall(xen_selfballoon_init);
-
-MODULE_LICENSE("GPL");
+EXPORT_SYMBOL(xen_selfballoon_init);
diff --git a/include/xen/tmem.h b/include/xen/tmem.h
index 591550a..3930a90 100644
--- a/include/xen/tmem.h
+++ b/include/xen/tmem.h
@@ -3,7 +3,15 @@
#include <linux/types.h>
+#ifdef CONFIG_XEN_TMEM_MODULE
+#define tmem_enabled true
+#else
/* defined in drivers/xen/tmem.c */
extern bool tmem_enabled;
+#endif
+
+#ifdef CONFIG_XEN_SELFBALLOONING
+extern int xen_selfballoon_init(bool, bool);
+#endif
#endif /* _XEN_TMEM_H */
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 11/11] zcache/tmem: Better error checking on frontswap_register_ops return value.
2013-02-15 20:20 [PATCH v3] Make frontswap+cleancache and its friend be modularized Konrad Rzeszutek Wilk
` (9 preceding siblings ...)
2013-02-15 20:20 ` [PATCH 10/11] xen: tmem: enable Xen tmem shim to be built/loaded as a module Konrad Rzeszutek Wilk
@ 2013-02-15 20:20 ` Konrad Rzeszutek Wilk
10 siblings, 0 replies; 12+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-02-15 20:20 UTC (permalink / raw)
To: dan.magenheimer, sjenning, gregkh, akpm, ngupta, rcj, linux-mm,
linux-kernel, devel, minchan
Cc: ric.masonn, lliubbo, Konrad Rzeszutek Wilk
In the past it either used to be NULL or the "older" backend. Now we
also return -Exx error codes.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/staging/zcache/zcache-main.c | 5 ++++-
drivers/xen/tmem.c | 5 ++++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 3554987..48e46c5 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -2006,8 +2006,11 @@ static int __init zcache_init(void)
namestr, frontswap_has_exclusive_gets,
!disable_frontswap_ignore_nonactive);
#endif
- if (old_ops != NULL)
+ if (IS_ERR(old_ops) || old_ops) {
+ if (IS_ERR(old_ops))
+ return PTR_RET(old_ops);
pr_warn("%s: frontswap_ops overridden\n", namestr);
+ }
}
if (ramster_enabled)
ramster_init(!disable_cleancache, !disable_frontswap,
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 9a4a9ec..2f939e5 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -395,8 +395,11 @@ static int xen_tmem_init(void)
frontswap_register_ops(&tmem_frontswap_ops);
tmem_frontswap_poolid = -1;
- if (old_ops)
+ if (IS_ERR(old_ops) || old_ops) {
+ if (IS_ERR(old_ops))
+ return PTR_ERR(old_ops);
s = " (WARNING: frontswap_ops overridden)";
+ }
printk(KERN_INFO "frontswap enabled, RAM provided by "
"Xen Transcendent Memory\n");
}
--
1.8.0.2
^ permalink raw reply related [flat|nested] 12+ messages in thread