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Message-Id: <1360959635-18922-6-git-send-email-konrad.wilk@oracle.com>
Date: Fri, 15 Feb 2013 15:20:29 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: dan.magenheimer@...cle.com, sjenning@...ux.vnet.ibm.com,
gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
ngupta@...are.org, rcj@...ux.vnet.ibm.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
minchan@...nel.org
Cc: ric.masonn@...il.com, lliubbo@...il.com,
Konrad Rzeszutek Wilk <konrad@...nok.org>
Subject: [PATCH 05/11] frontswap: Get rid of swap_lock dependency
From: Minchan Kim <minchan@...nel.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@...cle.com>
Signed-off-by: Minchan Kim <minchan@...nel.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@...ux.vnet.ibm.com>]
Signed-off-by: Konrad Rzeszutek Wilk <konrad@...nok.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
--
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