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>
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 2760b0f..538367e 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -121,8 +121,13 @@
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 @@
/*
* 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);