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Subject[PATCH v2 2/4] mm/hwpoison: remove race consideration
Date
From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Now memory_failure() and unpoison_memory() are protected by mf_mutex,
so no need to explicitly check races between them. So remove them.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
mm/memory-failure.c | 37 -------------------------------------
1 file changed, 37 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 97297edfbd8e..a47b741ca04b 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1507,14 +1507,6 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
lock_page(head);
page_flags = head->flags;

- if (!PageHWPoison(head)) {
- pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
- num_poisoned_pages_dec();
- unlock_page(head);
- put_page(head);
- return 0;
- }
-
/*
* TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
* simply disable it. In order to make it work properly, we need
@@ -1789,16 +1781,6 @@ int memory_failure(unsigned long pfn, int flags)
*/
page_flags = p->flags;

- /*
- * unpoison always clear PG_hwpoison inside page lock
- */
- if (!PageHWPoison(p)) {
- pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
- num_poisoned_pages_dec();
- unlock_page(p);
- put_page(p);
- goto unlock_mutex;
- }
if (hwpoison_filter(p)) {
if (TestClearPageHWPoison(p))
num_poisoned_pages_dec();
@@ -2016,17 +1998,6 @@ int unpoison_memory(unsigned long pfn)
goto unlock_mutex;
}

- /*
- * unpoison_memory() can encounter thp only when the thp is being
- * worked by memory_failure() and the page lock is not held yet.
- * In such case, we yield to memory_failure() and make unpoison fail.
- */
- if (!PageHuge(page) && PageTransHuge(page)) {
- unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
- pfn, &unpoison_rs);
- goto unlock_mutex;
- }
-
if (!get_hwpoison_page(p, flags)) {
if (TestClearPageHWPoison(p))
num_poisoned_pages_dec();
@@ -2035,20 +2006,12 @@ int unpoison_memory(unsigned long pfn)
goto unlock_mutex;
}

- lock_page(page);
- /*
- * This test is racy because PG_hwpoison is set outside of page lock.
- * That's acceptable because that won't trigger kernel panic. Instead,
- * the PG_hwpoison page will be caught and isolated on the entrance to
- * the free buddy page pool.
- */
if (TestClearPageHWPoison(page)) {
unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
pfn, &unpoison_rs);
num_poisoned_pages_dec();
freeit = 1;
}
- unlock_page(page);

put_page(page);
if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
--
2.25.1
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