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Subject[PATCH v2 1/4] mm/hwpoison: mf_mutex for soft offline and unpoison
Date
From: Naoya Horiguchi <naoya.horiguchi@nec.com>

Originally mf_mutex is introduced to serialize multiple MCE events, but
it's also helpful to exclude races among soft_offline_page() and
unpoison_memory(). So apply mf_mutex to them.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
ChangeLog v2:
- add mutex_unlock() in "page already poisoned" path in soft_offline_page().
(Thanks to Ding Hui)
---
mm/memory-failure.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index fa9dda95a2a2..97297edfbd8e 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1628,6 +1628,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
return rc;
}

+static DEFINE_MUTEX(mf_mutex);
+
/**
* memory_failure - Handle memory failure of a page.
* @pfn: Page Number of the corrupted page
@@ -1654,7 +1656,6 @@ int memory_failure(unsigned long pfn, int flags)
int res = 0;
unsigned long page_flags;
bool retry = true;
- static DEFINE_MUTEX(mf_mutex);

if (!sysctl_memory_failure_recovery)
panic("Memory failure on page %lx", pfn);
@@ -1978,6 +1979,7 @@ int unpoison_memory(unsigned long pfn)
struct page *page;
struct page *p;
int freeit = 0;
+ int ret = 0;
unsigned long flags = 0;
static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
@@ -1988,28 +1990,30 @@ int unpoison_memory(unsigned long pfn)
p = pfn_to_page(pfn);
page = compound_head(p);

+ mutex_lock(&mf_mutex);
+
if (!PageHWPoison(p)) {
unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

if (page_count(page) > 1) {
unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

if (page_mapped(page)) {
unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

if (page_mapping(page)) {
unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

/*
@@ -2020,7 +2024,7 @@ int unpoison_memory(unsigned long pfn)
if (!PageHuge(page) && PageTransHuge(page)) {
unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

if (!get_hwpoison_page(p, flags)) {
@@ -2028,7 +2032,7 @@ int unpoison_memory(unsigned long pfn)
num_poisoned_pages_dec();
unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
pfn, &unpoison_rs);
- return 0;
+ goto unlock_mutex;
}

lock_page(page);
@@ -2050,7 +2054,9 @@ int unpoison_memory(unsigned long pfn)
if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
put_page(page);

- return 0;
+unlock_mutex:
+ mutex_unlock(&mf_mutex);
+ return ret;
}
EXPORT_SYMBOL(unpoison_memory);

@@ -2231,9 +2237,12 @@ int soft_offline_page(unsigned long pfn, int flags)
return -EIO;
}

+ mutex_lock(&mf_mutex);
+
if (PageHWPoison(page)) {
pr_info("%s: %#lx page already poisoned\n", __func__, pfn);
put_ref_page(ref_page);
+ mutex_unlock(&mf_mutex);
return 0;
}

@@ -2251,5 +2260,7 @@ int soft_offline_page(unsigned long pfn, int flags)
}
}

+ mutex_unlock(&mf_mutex);
+
return ret;
}
--
2.25.1
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