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Subject[PATCH v3 4/8] mm/memory-failure.c: fix race with changing page more robustly
Date
We're only intended to deal with the non-Compound page after we split thp
in memory_failure. However, the page could have changed compound pages due
to race window. If this happens, we could retry once to hopefully handle
the page next round. Also remove unneeded orig_head. It's always equal to
the hpage. So we can use hpage directly and remove this redundant one.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/memory-failure.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 7e205d91b2d7..2ca50cfa601f 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1690,7 +1690,6 @@ int memory_failure(unsigned long pfn, int flags)
{
struct page *p;
struct page *hpage;
- struct page *orig_head;
struct dev_pagemap *pgmap;
int res = 0;
unsigned long page_flags;
@@ -1736,7 +1735,7 @@ int memory_failure(unsigned long pfn, int flags)
goto unlock_mutex;
}

- orig_head = hpage = compound_head(p);
+ hpage = compound_head(p);
num_poisoned_pages_inc();

/*
@@ -1817,10 +1816,21 @@ int memory_failure(unsigned long pfn, int flags)
lock_page(p);

/*
- * The page could have changed compound pages during the locking.
- * If this happens just bail out.
+ * We're only intended to deal with the non-Compound page here.
+ * However, the page could have changed compound pages due to
+ * race window. If this happens, we could try again to hopefully
+ * handle the page next round.
*/
- if (PageCompound(p) && compound_head(p) != orig_head) {
+ if (PageCompound(p)) {
+ if (retry) {
+ if (TestClearPageHWPoison(p))
+ num_poisoned_pages_dec();
+ unlock_page(p);
+ put_page(p);
+ flags &= ~MF_COUNT_INCREASED;
+ retry = false;
+ goto try_again;
+ }
action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
res = -EBUSY;
goto unlock_page;
--
2.23.0
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