+ mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memory-failure: send SIGBUS in the event of thp split fail
has been added to the -mm mm-unstable branch.  Its filename is
     mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jane Chu <jane.chu@oracle.com>
Subject: mm/memory-failure: send SIGBUS in the event of thp split fail
Date: Wed, 1 May 2024 17:24:58 -0600

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.

Link: https://lkml.kernel.org/r/20240501232458.3919593-4-jane.chu@oracle.com
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |   36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

--- a/mm/memory-failure.c~mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail
+++ a/mm/memory-failure.c
@@ -2162,6 +2162,37 @@ out:
 	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
@@ -2291,6 +2322,11 @@ try_again:
 		 */
 		folio_set_has_hwpoisoned(folio);
 		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;
 		}
_

Patches currently in -mm which might be from jane.chu@oracle.com are

mm-memory-failure-try-to-send-sigbus-even-if-unmap-failed.patch
mm-madvise-add-mf_action_required-to-madvisemadv_hwpoison.patch
mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail.patch