[PATCH v8 1/4] mm,hwpoison,hugetlb,memory_hotplug: hotremove memory section with hwpoisoned hugepage

From: Naoya Horiguchi
Date: Tue Oct 25 2022 - 01:18:10 EST

HWPoisoned page is not supposed to be accessed once marked, but currently
such accesses can happen during memory hotremove because do_migrate_range()
can be called before dissolve_free_huge_pages() is called.

Clear HPageMigratable for hwpoisoned hugepages to prevent them from being
migrated. This should be done in hugetlb_lock to avoid race against
isolate_hugetlb().

get_hwpoison_huge_page() needs to have a flag to show it's called from
unpoison to take refcount of hwpoisoned hugepages, so add it.

Reported-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
ChangeLog v7 -> v8:
- remove TestClearHPageMigratable and reduce to test and clear separately.

ChangeLog v3 -> v7:
- introduce TESTCLEARHPAGEFLAG() to determine the value of migratable_cleared

ChangeLog v3 -> v6:
- introduce migratable_cleared to remember that HPageMigratable is
cleared in error handling. It's needed to cancel when an error event
is filtered by hwpoison_filter(). (Thanks to Miaohe)

ChangeLog v2 -> v3
- move to the approach of clearing HPageMigratable instead of shifting
dissolve_free_huge_pages.
---
include/linux/hugetlb.h | 10 ++++++----
include/linux/mm.h | 6 ++++--
mm/hugetlb.c | 9 +++++----
mm/memory-failure.c | 21 +++++++++++++++++----
4 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index a899bc76d677..3568b90b397d 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -183,8 +183,9 @@ bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
long freed);
int isolate_hugetlb(struct page *page, struct list_head *list);
-int get_hwpoison_huge_page(struct page *page, bool *hugetlb);
-int get_huge_page_for_hwpoison(unsigned long pfn, int flags);
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison);
+int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared);
void putback_active_hugepage(struct page *page);
void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason);
void free_huge_page(struct page *page);
@@ -391,12 +392,13 @@ static inline int isolate_hugetlb(struct page *page, struct list_head *list)
return -EBUSY;
}

-static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+static inline int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison)
{
return 0;
}

-static inline int get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+static inline int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared)
{
return 0;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 58345f06a2f4..3da6283c9d30 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3246,9 +3246,11 @@ extern void shake_page(struct page *p);
extern atomic_long_t num_poisoned_pages __read_mostly;
extern int soft_offline_page(unsigned long pfn, int flags);
#ifdef CONFIG_MEMORY_FAILURE
-extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags);
+extern int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared);
#else
-static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+static inline int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared)
{
return 0;
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 931789a8f734..88d2dc756822 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7292,7 +7292,7 @@ int isolate_hugetlb(struct page *page, struct list_head *list)
return ret;
}

-int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
+int get_hwpoison_huge_page(struct page *page, bool *hugetlb, bool unpoison)
{
int ret = 0;

@@ -7302,7 +7302,7 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
*hugetlb = true;
if (HPageFreed(page))
ret = 0;
- else if (HPageMigratable(page))
+ else if (HPageMigratable(page) || unpoison)
ret = get_page_unless_zero(page);
else
ret = -EBUSY;
@@ -7311,12 +7311,13 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
return ret;
}

-int get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared)
{
int ret;

spin_lock_irq(&hugetlb_lock);
- ret = __get_huge_page_for_hwpoison(pfn, flags);
+ ret = __get_huge_page_for_hwpoison(pfn, flags, migratable_cleared);
spin_unlock_irq(&hugetlb_lock);
return ret;
}
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 62cf1e0fbc8e..0ba7032be8c0 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1250,7 +1250,7 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags)
int ret = 0;
bool hugetlb = false;

- ret = get_hwpoison_huge_page(head, &hugetlb);
+ ret = get_hwpoison_huge_page(head, &hugetlb, false);
if (hugetlb)
return ret;

@@ -1340,7 +1340,7 @@ static int __get_unpoison_page(struct page *page)
int ret = 0;
bool hugetlb = false;

- ret = get_hwpoison_huge_page(head, &hugetlb);
+ ret = get_hwpoison_huge_page(head, &hugetlb, true);
if (hugetlb)
return ret;

@@ -1791,7 +1791,8 @@ void hugetlb_clear_page_hwpoison(struct page *hpage)
* -EBUSY - the hugepage is busy (try to retry)
* -EHWPOISON - the hugepage is already hwpoisoned
*/
-int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
+int __get_huge_page_for_hwpoison(unsigned long pfn, int flags,
+ bool *migratable_cleared)
{
struct page *page = pfn_to_page(pfn);
struct page *head = compound_head(page);
@@ -1821,6 +1822,15 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
goto out;
}

+ /*
+ * Clearing HPageMigratable for hwpoisoned hugepages to prevent them
+ * from being migrated by memory hotremove.
+ */
+ if (count_increased && HPageMigratable(head)) {
+ ClearHPageMigratable(head);
+ *migratable_cleared = true;
+ }
+
return ret;
out:
if (count_increased)
@@ -1840,10 +1850,11 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
struct page *p = pfn_to_page(pfn);
struct page *head;
unsigned long page_flags;
+ bool migratable_cleared = false;

*hugetlb = 1;
retry:
- res = get_huge_page_for_hwpoison(pfn, flags);
+ res = get_huge_page_for_hwpoison(pfn, flags, &migratable_cleared);
if (res == 2) { /* fallback to normal page handling */
*hugetlb = 0;
return 0;
@@ -1867,6 +1878,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb

if (hwpoison_filter(p)) {
hugetlb_clear_page_hwpoison(head);
+ if (migratable_cleared)
+ SetHPageMigratable(head);
unlock_page(head);
if (res == 1)
put_page(head);
--
2.37.3.518.g79f2338b37