[PATCH 3/3] mm/memory-failure: send SIGBUS in the event of thp split fail

Jane Chu
2024-05-02T00:02:59Z

When handle hwpoison in a GUP longterm pin'ed thp page,
try_to_split_thp_page() will fail. And at this point, there is little else
the kernel could do except sending a SIGBUS to the user process, thus
give it a chance to recover.

Signed-off-by: Jane Chu <jane.chu@oracle.com>
---
mm/memory-failure.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 7fcf182abb96..67f4d24a98e7 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2168,6 +2168,37 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
return rc;
}

+/*
+ * The calling condition is as such: thp split failed, page might have
+ * been GUP longterm pinned, not much can be done for recovery.
+ * But a SIGBUS should be delivered with vaddr provided so that the user
+ * application has a chance to recover. Also, application processes'
+ * election for MCE early killed will be honored.
+ */
+static int kill_procs_now(struct page *p, unsigned long pfn, int flags,
+ struct page *hpage)
+{
+ struct folio *folio = page_folio(hpage);
+ LIST_HEAD(tokill);
+ int res = -EHWPOISON;
+
+ /* deal with user pages only */
+ if (PageReserved(p) || PageSlab(p) || PageTable(p) || PageOffline(p))
+ res = -EBUSY;
+ if (!(PageLRU(hpage) || PageHuge(p)))
+ res = -EBUSY;
+
+ if (res == -EHWPOISON) {
+ collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
+ kill_procs(&tokill, true, pfn, flags);
+ }
+
+ if (flags & MF_COUNT_INCREASED)
+ put_page(p);
+
+ return res;
+}
+
/**
* memory_failure - Handle memory failure of a page.
* @pfn: Page Number of the corrupted page
@@ -2297,6 +2328,11 @@ int memory_failure(unsigned long pfn, int flags)
*/
SetPageHasHWPoisoned(hpage);
if (try_to_split_thp_page(p) < 0) {
+ if (flags & MF_ACTION_REQUIRED) {
+ pr_err("%#lx: thp split failed\n", pfn);
+ res = kill_procs_now(p, pfn, flags, hpage);
+ goto unlock_mutex;
+ }
res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
goto unlock_mutex;
}
--
2.39.3