From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Originally mf_mutex is introduced to serialize multiple MCE events, but
it is not that useful to allow unpoison to run in parallel with memory_failure()
and soft offline. So apply mf_they to soft offline and unpoison.
The memory failure handler and soft offline handler get simpler with this.
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
---
ChangeLog v3:
- merge with "mm/hwpoison: remove race consideration"
- update description
ChangeLog v2:
- add mutex_unlock() in "page already poisoned" path in soft_offline_page().
(Thanks to Ding Hui)
---
mm/memory-failure.c | 62 +++++++++++++--------------------------------
1 file changed, 18 insertions(+), 44 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index e8c38e27b753..d29c79de6034 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
@@ -1628,6 +1620,8 @@ 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 +1648,6 @@ 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);
@@ -1788,16 +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();
@@ -1978,6 +1961,7 @@ 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);
@@ -1988,39 +1972,30 @@ 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;
- }
-
- /*
- * 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);
- return 0;
+ goto unlock_mutex;
}
if (!get_hwpoison_page(p, flags)) {
@@ -2028,29 +2003,23 @@ 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);
- /*
- * 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))
put_page(page);
- return 0;
+unlock_mutex:
+ mutex_unlock(&mf_mutex);
+ return ret;
}
EXPORT_SYMBOL(unpoison_memory);
@@ -2231,9 +2200,12 @@ 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 +2223,7 @@ int soft_offline_page(unsigned long pfn, int flags)
}
}
+ mutex_unlock(&mf_mutex);
+
return ret;
}
--
2.25.1
