From: Minchan Kim <minc...@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 unncessary swap_lock dependency.
Cc: Dan Magenheimer <dan.magenhei...@oracle.com>
Signed-off-by: Minchan Kim <minc...@kernel.org>
[v1: Rebased on my branch, reworked to work with backends loading late]
[v2: Added a check for !map]
Signed-off-by: Konrad Rzeszutek Wilk <kon...@darnok.org>
squash
---
include/linux/frontswap.h | 6 +++---
mm/frontswap.c | 12 +++++++++---
mm/swapfile.c | 7 ++++++-
3 files changed, 18 insertions(+), 7 deletions(-)
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 612c176..3d72f14 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..8254a6a 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];
+ /* enable_swap_info _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
@@ -166,14 +171,15 @@ 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)
+ if (!map)
return;
+ frontswap_map_set(sis, map);
frontswap_ops->init(type);
}
else {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index e97a0e5..c1c3a62 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1454,6 +1454,10 @@ static void _enable_swap_info(struct swap_info_struct
*p, int prio,
else
p->prio = --least_priority;
p->swap_map = swap_map;
+ /*
+ * This is required for frontswap to handle backends loading
+ * after the swap has been activated.
+ */
frontswap_map_set(p, frontswap_map);
p->flags |= SWP_WRITEOK;
nr_swap_pages += p->pages;
@@ -1477,9 +1481,9 @@ 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);
spin_unlock(&swap_lock);
}
@@ -1589,6 +1593,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
p->swap_map = NULL;
p->flags = 0;
frontswap_invalidate_area(type);
+ frontswap_map_set(p, NULL);
spin_unlock(&swap_lock);
mutex_unlock(&swapon_mutex);
vfree(swap_map);
--
1.7.11.7
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