mm,hwpoison: Try to narrow window race for free pages

mainline inclusion
from linux-v5.10-rc1
commit b94e0282
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4LE22
CVE: NA

--------------------------------

Aristeu Rozanski reported that a customer test case started
to report -EBUSY after the hwpoison rework patchset.

There is a race window between spotting a free page and taking it off
its buddy freelist, so it might be that by the time we try to take it off,
the page has been already allocated.

This patch tries to handle such race window by trying to handle the new
type of page again if the page was allocated under us.
Signed-off-by: NOscar Salvador <osalvador@suse.de>
Reported-by: NAristeu Rozanski <aris@ruivo.org>
Tested-by: NAristeu Rozanski <aris@ruivo.org>
Acked-by: NNaoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: NMa Wupeng <mawupeng1@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

mm/memory-failure.c

@@ -1892,6 +1892,7 @@ int soft_offline_page(struct page *page, int flags)
 {
 	int ret;
 	unsigned long pfn = page_to_pfn(page);
+	bool try_again = true;
 
 	if (is_zone_device_page(page)) {
 		pr_debug_ratelimited("soft_offline: %#lx page is device page\n",
@@ -1908,6 +1909,7 @@ int soft_offline_page(struct page *page, int flags)
 		return 0;
 	}
 
+retry:
 	get_online_mems();
 	ret = get_any_page(page, pfn, flags);
 	put_online_mems();
@@ -1915,7 +1917,10 @@ int soft_offline_page(struct page *page, int flags)
 	if (ret > 0)
 		ret = soft_offline_in_use_page(page);
 	else if (ret == 0)
-		ret = soft_offline_free_page(page);
+		if (soft_offline_free_page(page) && try_again) {
+			try_again = false;
+			goto retry;
+		}
 
 	return ret;
 }