+ mm-swapfile-add-cond_resched-in-get_swap_pages.patch added to mm-hotfixes-unstable branch

+ mm-swapfile-add-cond_resched-in-get_swap_pages.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/swapfile: add cond_resched() in get_swap_pages()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-swapfile-add-cond_resched-in-get_swap_pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swapfile-add-cond_resched-in-get_swap_pages.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Longlong Xia <xialonglong1@huawei.com>
Subject: mm/swapfile: add cond_resched() in get_swap_pages()
Date: Sat, 28 Jan 2023 09:47:57 +0000

The softlockup still occurs in get_swap_pages() under memory pressure.  64
CPU cores, 64GB memory, and 28 zram devices, the disksize of each zram
device is 50MB with same priority as si.  Use the stress-ng tool to
increase memory pressure, causing the system to oom frequently.

The plist_for_each_entry_safe() loops in get_swap_pages() could reach tens
of thousands of times to find available space (extreme case:
cond_resched() is not called in scan_swap_map_slots()).  Let's add
cond_resched() into get_swap_pages() when failed to find available space
to avoid softlockup.

Link: https://lkml.kernel.org/r/20230128094757.1060525-1-xialonglong1@huawei.com
Signed-off-by: Longlong Xia <xialonglong1@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Chen Wandun <chenwandun@huawei.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/swapfile.c~mm-swapfile-add-cond_resched-in-get_swap_pages
+++ a/mm/swapfile.c
@@ -1100,6 +1100,7 @@ start_over:
 			goto check_out;
 		pr_debug("scan_swap_map of si %d failed to find offset\n",
 			si->type);
+		cond_resched();
 
 		spin_lock(&swap_avail_lock);
 nextsi:
_

Patches currently in -mm which might be from xialonglong1@huawei.com are

mm-swapfile-add-cond_resched-in-get_swap_pages.patch