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Commit 69217b4c authored by Sasha Levin's avatar Sasha Levin Committed by Konrad Rzeszutek Wilk
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mm: frontswap: split frontswap_shrink further to simplify locking 



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: default avatarSasha Levin <levinsasha928@gmail.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent f116695a

mm/frontswap.c

+21 −15
Original line number Original line Diff line number Diff line
@@ -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);

	if (ret == 0 && pages_to_unuse)

		try_to_unuse(type, true, pages_to_unuse);

		try_to_unuse(type, true, pages_to_unuse);

out:

	if (locked)

		spin_unlock(&swap_lock);

	return;

	return;

}

}

EXPORT_SYMBOL(frontswap_shrink);

EXPORT_SYMBOL(frontswap_shrink);