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authorMinchan Kim <minchan@kernel.org>2013-04-30 15:26:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-30 17:04:00 -0700
commit4f89849da22db9d0edb378acea65e23fcd546173 (patch)
tree8af95a340c8d8605ad8f492ef0f6f98f2a4e4523 /mm
parentf066ea230a65f939afc354beae62716ab5f0e645 (diff)
downloadlinux-4f89849da22db9d0edb378acea65e23fcd546173.tar.gz
frontswap: get rid of swap_lock dependency
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> Signed-off-by: Bob Liu <lliubbo@gmail.com> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Andor Daam <andor.daam@googlemail.com> Cc: Florian Schmaus <fschmaus@gmail.com> Cc: Stefan Hengelein <ilendir@googlemail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/frontswap.c31
-rw-r--r--mm/swapfile.c17
2 files changed, 32 insertions, 16 deletions
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 2760b0f9882..538367ef137 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -121,8 +121,13 @@ 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
@@ -156,20 +161,30 @@ EXPORT_SYMBOL(frontswap_tmem_exclusive_gets);
/*
* Called when a swap device is swapon'd.
*/
-void __frontswap_init(unsigned type)
+void __frontswap_init(unsigned type, unsigned long *map)
{
struct swap_info_struct *sis = swap_info[type];
- if (frontswap_ops) {
- 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 (frontswap_ops)
frontswap_ops->init(type);
- } else {
+ else {
BUG_ON(type > MAX_SWAPFILES);
set_bit(type, need_init);
}
-
}
EXPORT_SYMBOL(__frontswap_init);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index d417efddfe7..6c340d908b2 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1509,8 +1509,7 @@ 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;
@@ -1519,7 +1518,6 @@ 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;
atomic_long_add(p->pages, &nr_swap_pages);
total_swap_pages += p->pages;
@@ -1542,10 +1540,10 @@ 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);
spin_lock(&p->lock);
- _enable_swap_info(p, prio, swap_map, frontswap_map);
- frontswap_init(p->type);
+ _enable_swap_info(p, prio, swap_map);
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
}
@@ -1554,7 +1552,7 @@ static void reinsert_swap_info(struct swap_info_struct *p)
{
spin_lock(&swap_lock);
spin_lock(&p->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(&p->lock);
spin_unlock(&swap_lock);
}
@@ -1563,6 +1561,7 @@ 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;
@@ -1662,12 +1661,14 @@ 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(&p->lock);
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);