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frontswap: get rid of swap_lock dependency

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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 <[email protected]>
Signed-off-by: Minchan Kim <[email protected]>
[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 <[email protected]>]
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Bob Liu <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Andor Daam <[email protected]>
Cc: Florian Schmaus <[email protected]>
Cc: Stefan Hengelein <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Minchan Kim 2013-04-30 15:26:54 -07:00 • committed by Linus Torvalds
commit 4f89849da2
3 changed files with 35 additions and 19 deletions
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31
mm/frontswap.c
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@ -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);