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authorOscar Salvador <osalvador@suse.de>2020-10-15 20:07:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-16 11:11:16 -0700
commit79f5f8fab482dfff62948214468ac4ebbf0a016f (patch)
treee45a327a0997a008b620c010735b0c833668c541
parent06be6ff3d2ec8be806b859fc054a1909b16d2473 (diff)
mm,hwpoison: rework soft offline for in-use pages
This patch changes the way we set and handle in-use poisoned pages. Until now, poisoned pages were released to the buddy allocator, trusting that the checks that take place at allocation time would act as a safe net and would skip that page. This has proved to be wrong, as we got some pfn walkers out there, like compaction, that all they care is the page to be in a buddy freelist. Although this might not be the only user, having poisoned pages in the buddy allocator seems a bad idea as we should only have free pages that are ready and meant to be used as such. Before explaining the taken approach, let us break down the kind of pages we can soft offline. - Anonymous THP (after the split, they end up being 4K pages) - Hugetlb - Order-0 pages (that can be either migrated or invalited) * Normal pages (order-0 and anon-THP) - If they are clean and unmapped page cache pages, we invalidate then by means of invalidate_inode_page(). - If they are mapped/dirty, we do the isolate-and-migrate dance. Either way, do not call put_page directly from those paths. Instead, we keep the page and send it to page_handle_poison to perform the right handling. page_handle_poison sets the HWPoison flag and does the last put_page. Down the chain, we placed a check for HWPoison page in free_pages_prepare, that just skips any poisoned page, so those pages do not end up in any pcplist/freelist. After that, we set the refcount on the page to 1 and we increment the poisoned pages counter. If we see that the check in free_pages_prepare creates trouble, we can always do what we do for free pages: - wait until the page hits buddy's freelists - take it off, and flag it The downside of the above approach is that we could race with an allocation, so by the time we want to take the page off the buddy, the page has been already allocated so we cannot soft offline it. But the user could always retry it. * Hugetlb pages - We isolate-and-migrate them After the migration has been successful, we call dissolve_free_huge_page, and we set HWPoison on the page if we succeed. Hugetlb has a slightly different handling though. While for non-hugetlb pages we cared about closing the race with an allocation, doing so for hugetlb pages requires quite some additional and intrusive code (we would need to hook in free_huge_page and some other places). So I decided to not make the code overly complicated and just fail normally if the page we allocated in the meantime. We can always build on top of this. As a bonus, because of the way we handle now in-use pages, we no longer need the put-as-isolation-migratetype dance, that was guarding for poisoned pages to end up in pcplists. Signed-off-by: Oscar Salvador <osalvador@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Cc: Aristeu Rozanski <aris@ruivo.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Dmitry Yakunin <zeil@yandex-team.ru> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Oscar Salvador <osalvador@suse.com> Cc: Qian Cai <cai@lca.pw> Cc: Tony Luck <tony.luck@intel.com> Link: https://lkml.kernel.org/r/20200922135650.1634-10-osalvador@suse.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/page-flags.h5
-rw-r--r--mm/memory-failure.c43
-rw-r--r--mm/migrate.c11
-rw-r--r--mm/page_alloc.c39
4 files changed, 28 insertions, 70 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index a02b6d0221db..4f6ba9379112 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -431,14 +431,9 @@ PAGEFLAG_FALSE(Uncached)
PAGEFLAG(HWPoison, hwpoison, PF_ANY)
TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
#define __PG_HWPOISON (1UL << PG_hwpoison)
-extern bool set_hwpoison_free_buddy_page(struct page *page);
extern bool take_page_off_buddy(struct page *page);
#else
PAGEFLAG_FALSE(HWPoison)
-static inline bool set_hwpoison_free_buddy_page(struct page *page)
-{
- return 0;
-}
#define __PG_HWPOISON 0
#endif
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index af7fb23b93ae..962129c50be2 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -65,9 +65,11 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
-static void page_handle_poison(struct page *page)
+static void page_handle_poison(struct page *page, bool release)
{
SetPageHWPoison(page);
+ if (release)
+ put_page(page);
page_ref_inc(page);
num_poisoned_pages_inc();
}
@@ -1765,19 +1767,13 @@ static int soft_offline_huge_page(struct page *page, int flags)
ret = -EIO;
} else {
/*
- * We set PG_hwpoison only when the migration source hugepage
- * was successfully dissolved, because otherwise hwpoisoned
- * hugepage remains on free hugepage list, then userspace will
- * find it as SIGBUS by allocation failure. That's not expected
- * in soft-offlining.
+ * We set PG_hwpoison only when we were able to take the page
+ * off the buddy.
*/
- ret = dissolve_free_huge_page(page);
- if (!ret) {
- if (set_hwpoison_free_buddy_page(page))
- num_poisoned_pages_inc();
- else
- ret = -EBUSY;
- }
+ if (!dissolve_free_huge_page(page) && take_page_off_buddy(page))
+ page_handle_poison(page, false);
+ else
+ ret = -EBUSY;
}
return ret;
}
@@ -1812,10 +1808,8 @@ static int __soft_offline_page(struct page *page, int flags)
* would need to fix isolation locking first.
*/
if (ret == 1) {
- put_page(page);
pr_info("soft_offline: %#lx: invalidated\n", pfn);
- SetPageHWPoison(page);
- num_poisoned_pages_inc();
+ page_handle_poison(page, true);
return 0;
}
@@ -1846,7 +1840,9 @@ static int __soft_offline_page(struct page *page, int flags)
list_add(&page->lru, &pagelist);
ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
MIGRATE_SYNC, MR_MEMORY_FAILURE);
- if (ret) {
+ if (!ret) {
+ page_handle_poison(page, true);
+ } else {
if (!list_empty(&pagelist))
putback_movable_pages(&pagelist);
@@ -1865,27 +1861,16 @@ static int __soft_offline_page(struct page *page, int flags)
static int soft_offline_in_use_page(struct page *page, int flags)
{
int ret;
- int mt;
struct page *hpage = compound_head(page);
if (!PageHuge(page) && PageTransHuge(hpage))
if (try_to_split_thp_page(page, "soft offline") < 0)
return -EBUSY;
- /*
- * Setting MIGRATE_ISOLATE here ensures that the page will be linked
- * to free list immediately (not via pcplist) when released after
- * successful page migration. Otherwise we can't guarantee that the
- * page is really free after put_page() returns, so
- * set_hwpoison_free_buddy_page() highly likely fails.
- */
- mt = get_pageblock_migratetype(page);
- set_pageblock_migratetype(page, MIGRATE_ISOLATE);
if (PageHuge(page))
ret = soft_offline_huge_page(page, flags);
else
ret = __soft_offline_page(page, flags);
- set_pageblock_migratetype(page, mt);
return ret;
}
@@ -1894,7 +1879,7 @@ static int soft_offline_free_page(struct page *page)
int rc = -EBUSY;
if (!dissolve_free_huge_page(page) && take_page_off_buddy(page)) {
- page_handle_poison(page);
+ page_handle_poison(page, false);
rc = 0;
}
diff --git a/mm/migrate.c b/mm/migrate.c
index f94d7c7eeddf..4cf1af88c1dd 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1223,16 +1223,11 @@ out:
* we want to retry.
*/
if (rc == MIGRATEPAGE_SUCCESS) {
- put_page(page);
- if (reason == MR_MEMORY_FAILURE) {
+ if (reason != MR_MEMORY_FAILURE)
/*
- * Set PG_HWPoison on just freed page
- * intentionally. Although it's rather weird,
- * it's how HWPoison flag works at the moment.
+ * We release the page in page_handle_poison.
*/
- if (set_hwpoison_free_buddy_page(page))
- num_poisoned_pages_inc();
- }
+ put_page(page);
} else {
if (rc != -EAGAIN) {
if (likely(!__PageMovable(page))) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 12dcfb3dc588..7fa55d9a3fe4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1174,6 +1174,17 @@ static __always_inline bool free_pages_prepare(struct page *page,
trace_mm_page_free(page, order);
+ if (unlikely(PageHWPoison(page)) && !order) {
+ /*
+ * Do not let hwpoison pages hit pcplists/buddy
+ * Untie memcg state and reset page's owner
+ */
+ if (memcg_kmem_enabled() && PageKmemcg(page))
+ __memcg_kmem_uncharge_page(page, order);
+ reset_page_owner(page, order);
+ return false;
+ }
+
/*
* Check tail pages before head page information is cleared to
* avoid checking PageCompound for order-0 pages.
@@ -8844,32 +8855,4 @@ bool take_page_off_buddy(struct page *page)
spin_unlock_irqrestore(&zone->lock, flags);
return ret;
}
-
-/*
- * Set PG_hwpoison flag if a given page is confirmed to be a free page. This
- * test is performed under the zone lock to prevent a race against page
- * allocation.
- */
-bool set_hwpoison_free_buddy_page(struct page *page)
-{
- struct zone *zone = page_zone(page);
- unsigned long pfn = page_to_pfn(page);
- unsigned long flags;
- unsigned int order;
- bool hwpoisoned = false;
-
- spin_lock_irqsave(&zone->lock, flags);
- for (order = 0; order < MAX_ORDER; order++) {
- struct page *page_head = page - (pfn & ((1 << order) - 1));
-
- if (PageBuddy(page_head) && page_order(page_head) >= order) {
- if (!TestSetPageHWPoison(page))
- hwpoisoned = true;
- break;
- }
- }
- spin_unlock_irqrestore(&zone->lock, flags);
-
- return hwpoisoned;
-}
#endif