Patch "swap: cond_resched in swap_cgroup_prepare()" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

swap: cond_resched in swap_cgroup_prepare()

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
swap-cond_resched-in-swap_cgroup_prepare.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yu Zhao <[email protected]>
Date: Fri, 16 Jun 2017 14:02:31 -0700
Subject: swap: cond_resched in swap_cgroup_prepare()

From: Yu Zhao <[email protected]>

commit ef70762948dde012146926720b70e79736336764 upstream.

I saw need_resched() warnings when swapping on large swapfile (TBs) because continuously allocating many pages in swap_cgroup_prepare() took too long.

We already cond_resched when freeing page in swap_cgroup_swapoff(). Do the same for the page allocation.

---
 mm/swap_cgroup.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -48,6 +48,9 @@ static int swap_cgroup_prepare(int type)
 		if (!page)
 			goto not_enough_page;
 		ctrl->map[idx] = page;
+
+		if (!(idx % SWAP_CLUSTER_MAX))
+			cond_resched();
 	}
 	return 0;
 not_enough_page:

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/swap-cond_resched-in-swap_cgroup_prepare.patch