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@xxxxxxxxxx>
Subject: mm/memory-failure: send SIGBUS in the event of thp split fail
Date: Tue, 21 May 2024 17:54:29 -0600
While handling hwpoison in a THP page, it is possible that
try_to_split_thp_page() fails. For example, when the THP page has been
RDMA pinned. At this point, the kernel cannot isolate the poisoned THP
page, all it could do is to send a SIGBUS to the user process with
meaningful payload to give user-level recovery a chance.
Link: https://lkml.kernel.org/r/20240521235429.2368017-6-jane.chu@xxxxxxxxxx
Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx>
Cc: Oscar Salvador <oalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
--- a/mm/memory-failure.c~mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail
+++ a/mm/memory-failure.c
@@ -1706,7 +1706,12 @@ static int identify_page_state(unsigned
return page_action(ps, p, pfn);
}
-static int try_to_split_thp_page(struct page *page)
+/*
+ * When 'release' is 'false', it means that if thp split has failed,
+ * there is still more to do, hence the page refcount we took earlier
+ * is still needed.
+ */
+static int try_to_split_thp_page(struct page *page, bool release)
{
int ret;
@@ -1714,7 +1719,7 @@ static int try_to_split_thp_page(struct
ret = split_huge_page(page);
unlock_page(page);
- if (unlikely(ret))
+ if (ret && release)
put_page(page);
return ret;
@@ -2187,6 +2192,24 @@ out:
return rc;
}
+/*
+ * The calling condition is as such: thp split failed, page might have
+ * been RDMA 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 folio *folio)
+{
+ LIST_HEAD(tokill);
+
+ collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
+ kill_procs(&tokill, true, pfn, flags);
+
+ return -EHWPOISON;
+}
+
/**
* memory_failure - Handle memory failure of a page.
* @pfn: Page Number of the corrupted page
@@ -2328,8 +2351,10 @@ try_again:
* page is a valid handlable page.
*/
folio_set_has_hwpoisoned(folio);
- if (try_to_split_thp_page(p) < 0) {
- res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
+ if (try_to_split_thp_page(p, false) < 0) {
+ res = kill_procs_now(p, pfn, flags, folio);
+ put_page(p);
+ action_result(pfn, MF_MSG_UNSPLIT_THP, MF_FAILED);
goto unlock_mutex;
}
VM_BUG_ON_PAGE(!page_count(p), p);
@@ -2710,7 +2735,7 @@ static int soft_offline_in_use_page(stru
};
if (!huge && folio_test_large(folio)) {
- if (try_to_split_thp_page(page)) {
+ if (try_to_split_thp_page(page, true)) {
pr_info("soft offline: %#lx: thp split failed\n", pfn);
return -EBUSY;
}
_
Patches currently in -mm which might be from jane.chu@xxxxxxxxxx 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-improve-memory-failure-action_result-messages.patch
mm-memory-failure-move-hwpoison_filter-higher-up.patch
mm-memory-failure-send-sigbus-in-the-event-of-thp-split-fail.patch
