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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/frontswap.c
parentf066ea230a65f939afc354beae62716ab5f0e645 (diff)
downloadlwn-4f89849da22db9d0edb378acea65e23fcd546173.tar.gz
lwn-4f89849da22db9d0edb378acea65e23fcd546173.zip
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/frontswap.c')
-rw-r--r--mm/frontswap.c31
1 files changed, 23 insertions, 8 deletions
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 2760b0f98822..538367ef1372 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);