From 8d7483174458577ca1b8134de7669a0ddef8c86b Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Tue, 30 Jun 2026 05:46:04 -0700 Subject: [PATCH] mm/memory-failure: drop dead error_states[] entry for reserved pages MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Patch series "mm/memory-failure: add panic option for unrecoverable pages", v10. A multi-bit ECC error on a kernel-owned page that the memory failure handler cannot recover is currently swallowed: PG_hwpoison is set, the event is logged, and the kernel keeps running. The corrupted memory remains accessible to the kernel and either drives silent data corruption or surfaces seconds-to-minutes later as an apparently unrelated crash. In a large fleet that delayed, unattributable crash turns into significant engineering effort to root-cause; in a kdump configuration, by the time the crash happens the original error context (faulting PFN, MCE/GHES record, page state) is long gone. This series adds an opt-in sysctl, vm.panic_on_unrecoverable_memory_failure, that converts an unrecoverable kernel-page hwpoison event into an immediate panic with a clean dmesg/vmcore that still contains the original failure context. The default is disabled so existing workloads see no change. There is a selftest that test different cases, and I tested it using the following variants: ┌─────────┬──────────┬───────────────────────────────────────────────────────────┐ │ Variant │ PFN │ Result │ ├─────────┼──────────┼───────────────────────────────────────────────────────────┤ │ rodata │ 0x2600 │ Panic with "Memory failure: 0x2600: unrecoverable page" │ ├─────────┼──────────┼───────────────────────────────────────────────────────────┤ │ slab │ 0x100032 │ Panic with "Memory failure: 0x100032: unrecoverable page" │ ├─────────┼──────────┼───────────────────────────────────────────────────────────┤ │ pgtable │ 0x100000 │ Panic with "Memory failure: 0x100000: unrecoverable page" │ └─────────┴──────────┴───────────────────────────────────────────────────────────┘ Each one shows the same call trace, exactly the path the series builds: hard_offline_page_store → memory_failure → action_result → panic("Memory failure: %#lx: unrecoverable page") This patch (of 5): The first entry of error_states[], { reserved, reserved, MF_MSG_KERNEL, me_kernel }, is unreachable. identify_page_state() has two callers, and neither one can dispatch a PG_reserved page to me_kernel(): * memory_failure() reaches identify_page_state() only after get_hwpoison_page() returned 1. get_any_page() reaches that return only via __get_hwpoison_page(), which only takes a refcount when the page is HWPoisonHandlable(). HWPoisonHandlable() is an allowlist for LRU, free-buddy, and (for soft-offline) movable_ops pages -- PG_reserved pages do not satisfy any of these, so they fail with -EBUSY/-EIO long before identify_page_state() runs. * try_memory_failure_hugetlb() reaches identify_page_state() only via the MF_HUGETLB_IN_USED branch, where the page is necessarily a hugetlb folio. hugetlb folios don't carry PG_reserved at that point: hugetlb_folio_init_vmemmap() calls __folio_clear_reserved() during init, so the reserved entry would not match even if it were still present. me_kernel() never executes and the entry exists only to be matched against by code that cannot see it. Drop the entry, the me_kernel() helper, and the now-unused "reserved" macro. Leave the MF_MSG_KERNEL enum value in place: it remains part of the tracepoint and pr_err() string tables, and follow-on work to classify unrecoverable kernel pages can reuse it without churning the user-visible enum. No functional change. Link: https://lore.kernel.org/20260630-ecc_panic-v10-0-c6ed5b62eea2@debian.org Link: https://lore.kernel.org/20260630-ecc_panic-v10-1-c6ed5b62eea2@debian.org Signed-off-by: Breno Leitao Suggested-by: David Hildenbrand Acked-by: David Hildenbrand (Arm) Reviewed-by: Lance Yang Acked-by: Miaohe Lin Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Michal Hocko Cc: Mike Rapoport Cc: Naoya Horiguchi Cc: Shuah Khan Cc: Steven Rostedt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/memory-failure.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 1fb4f6206e6b..12efd03dc0ec 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -981,17 +981,6 @@ static bool has_extra_refcount(struct page_state *ps, struct page *p, return false; } -/* - * Error hit kernel page. - * Do nothing, try to be lucky and not touch this instead. For a few cases we - * could be more sophisticated. - */ -static int me_kernel(struct page_state *ps, struct page *p) -{ - unlock_page(p); - return MF_IGNORED; -} - /* * Page in unknown state. Do nothing. * This is a catch-all in case we fail to make sense of the page state. @@ -1200,10 +1189,8 @@ static int me_huge_page(struct page_state *ps, struct page *p) #define mlock (1UL << PG_mlocked) #define lru (1UL << PG_lru) #define head (1UL << PG_head) -#define reserved (1UL << PG_reserved) static struct page_state error_states[] = { - { reserved, reserved, MF_MSG_KERNEL, me_kernel }, /* * free pages are specially detected outside this table: * PG_buddy pages only make a small fraction of all free pages. @@ -1235,7 +1222,6 @@ static struct page_state error_states[] = { #undef mlock #undef lru #undef head -#undef reserved static void update_per_node_mf_stats(unsigned long pfn, enum mf_result result)