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mm: frontswap: split frontswap_shrink further to simplify locking

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Split frontswap_shrink to simplify the locking in the original code.

Also, assert that the function that was split still runs under the
swap spinlock.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Sasha Levin 2012-06-10 12:51:03 +02:00 committed by Konrad Rzeszutek Wilk
parent f116695a50
commit 69217b4cd0
1 changed files with 21 additions and 15 deletions
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36
mm/frontswap.c
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@ -265,6 +265,24 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
return ret; return ret;
} }
static int __frontswap_shrink(unsigned long target_pages,
unsigned long *pages_to_unuse,
int *type)
{
unsigned long total_pages = 0, total_pages_to_unuse;
assert_spin_locked(&swap_lock);
total_pages = __frontswap_curr_pages();
if (total_pages <= target_pages) {
/* Nothing to do */
*pages_to_unuse = 0;
return 0;
}
total_pages_to_unuse = total_pages - target_pages;
return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
}
/* /*
* Frontswap, like a true swap device, may unnecessarily retain pages * Frontswap, like a true swap device, may unnecessarily retain pages
* under certain circumstances; "shrink" frontswap is essentially a * under certain circumstances; "shrink" frontswap is essentially a
@ -275,10 +293,8 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
*/ */
void frontswap_shrink(unsigned long target_pages) void frontswap_shrink(unsigned long target_pages)
{ {
unsigned long total_pages = 0, total_pages_to_unuse;
unsigned long pages_to_unuse = 0; unsigned long pages_to_unuse = 0;
int type, ret; int type, ret;
bool locked = false;
/* /*
* we don't want to hold swap_lock while doing a very * we don't want to hold swap_lock while doing a very
@ -286,20 +302,10 @@ void frontswap_shrink(unsigned long target_pages)
* so restart scan from swap_list.head each time * so restart scan from swap_list.head each time
*/ */
spin_lock(&swap_lock); spin_lock(&swap_lock);
locked = true; ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
total_pages = __frontswap_curr_pages();
if (total_pages <= target_pages)
goto out;
total_pages_to_unuse = total_pages - target_pages;
ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
if (ret < 0)
goto out;
locked = false;
spin_unlock(&swap_lock); spin_unlock(&swap_lock);
try_to_unuse(type, true, pages_to_unuse); if (ret == 0 && pages_to_unuse)
out: try_to_unuse(type, true, pages_to_unuse);
if (locked)
spin_unlock(&swap_lock);
return; return;
} }
EXPORT_SYMBOL(frontswap_shrink); EXPORT_SYMBOL(frontswap_shrink);