[pve-devel] applied: [PATCH kernel 4.13] fix #1633: potential deadlock with THPs

[Thomas Lamprecht]

applied to master and pve-kernel-4.15

On 3/26/18 2:42 PM, Fabian Grünbichler wrote:
> see https://marc.info/?l=linux-mm&m=151683828707588
> 
> Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
> ---
>  ...ot-wait-for-lock_page-in-deferred_split_s.patch | 46 ++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 patches/kernel/0022-mm-thp-Do-not-wait-for-lock_page-in-deferred_split_s.patch
> 
> diff --git a/patches/kernel/0022-mm-thp-Do-not-wait-for-lock_page-in-deferred_split_s.patch b/patches/kernel/0022-mm-thp-Do-not-wait-for-lock_page-in-deferred_split_s.patch
> new file mode 100644
> index 0000000..239aa42
> --- /dev/null
> +++ b/patches/kernel/0022-mm-thp-Do-not-wait-for-lock_page-in-deferred_split_s.patch
> @@ -0,0 +1,46 @@
> +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
> +From: "Kirill A. Shutemov" <kirill.shutemov at linux.intel.com>
> +Date: Thu, 15 Mar 2018 18:07:47 +0300
> +Subject: [PATCH] mm/thp: Do not wait for lock_page() in deferred_split_scan()
> +MIME-Version: 1.0
> +Content-Type: text/plain; charset=UTF-8
> +Content-Transfer-Encoding: 8bit
> +
> +deferred_split_scan() gets called from reclaim path. Waiting for page
> +lock may lead to deadlock there.
> +
> +Replace lock_page() with trylock_page() and skip the page if we failed
> +to lock it. We will get to the page on the next scan.
> +
> +Fixes: 9a982250f773 ("thp: introduce deferred_split_huge_page()")
> +
> +Signed-off-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
> +Acked-by: Michal Hocko <mhocko at suse.com>
> +(cherry-picked from https://patchwork.kernel.org/patch/10284703/)
> +Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
> +---
> + mm/huge_memory.c | 4 +++-
> + 1 file changed, 3 insertions(+), 1 deletion(-)
> +
> +diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> +index 8b887db33383..5c4093e0be8d 100644
> +--- a/mm/huge_memory.c
> ++++ b/mm/huge_memory.c
> +@@ -2621,11 +2621,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
> + 
> + 	list_for_each_safe(pos, next, &list) {
> + 		page = list_entry((void *)pos, struct page, mapping);
> +-		lock_page(page);
> ++		if (!trylock_page(page))
> ++			goto next;
> + 		/* split_huge_page() removes page from list on success */
> + 		if (!split_huge_page(page))
> + 			split++;
> + 		unlock_page(page);
> ++next:
> + 		put_page(page);
> + 	}
> + 
> +-- 
> +2.14.2
> +
>