On 5/22/2024 8:02 PM, Miaohe Lin wrote:
On 2024/5/22 7:54, Jane Chu wrote:
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.
Thanks for your patch.
Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
---
mm/memory-failure.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 794196951a04..a14d56e66902 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1706,7 +1706,12 @@ static int identify_page_state(unsigned long pfn, struct page *p,
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 page *page)
ret = split_huge_page(page);
unlock_page(page);
- if (unlikely(ret))
+ if (ret && release)
put_page(page);
Is "unlikely" still needed?
I'd say not, because this code is not on performance sensitive code path.
return ret;
@@ -2187,6 +2192,24 @@ 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 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 @@ int memory_failure(unsigned long pfn, int flags)
* 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);
No strong opinion but we might remove the return value of kill_procs_now as
it always return -EHWPOISON? We could simply set res to -EHWPOISON here.
I like that, will change.
Besides from above possible nits, this patch looks good to me.
Acked-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Thanks.
Thank!
-jane
.
