[115/227] mm/memory-failure.c: fix race with changing page more robustly

Commit Message

Andrew Morton March 22, 2022, 9:44 p.m. UTC

From: Miaohe Lin <[e-mail]>
Subject: mm/memory-failure.c: fix race with changing page more robustly

We're only intended to deal with the non-Compound page after we split thp
in memory_failure.  However, the page could have changed compound pages
due to race window.  If this happens, we could retry once to hopefully
handle the page next round.  Also remove unneeded orig_head.  It's always
equal to the hpage.  So we can use hpage directly and remove this
redundant one.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Miaohe Lin <[e-mail]>
Acked-by: Naoya Horiguchi <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memory-failure.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Patch

--- a/mm/memory-failure.c~mm-memory-failurec-fix-race-with-changing-page-more-robustly
+++ a/mm/memory-failure.c
@@ -1686,7 +1686,6 @@  int memory_failure(unsigned long pfn, in
 {
 	struct page *p;
 	struct page *hpage;
-	struct page *orig_head;
 	struct dev_pagemap *pgmap;
 	int res = 0;
 	unsigned long page_flags;
@@ -1732,7 +1731,7 @@  try_again:
 		goto unlock_mutex;
 	}
 
-	orig_head = hpage = compound_head(p);
+	hpage = compound_head(p);
 	num_poisoned_pages_inc();
 
 	/*
@@ -1813,10 +1812,21 @@  try_again:
 	lock_page(p);
 
 	/*
-	 * The page could have changed compound pages during the locking.
-	 * If this happens just bail out.
+	 * We're only intended to deal with the non-Compound page here.
+	 * However, the page could have changed compound pages due to
+	 * race window. If this happens, we could try again to hopefully
+	 * handle the page next round.
 	 */
-	if (PageCompound(p) && compound_head(p) != orig_head) {
+	if (PageCompound(p)) {
+		if (retry) {
+			if (TestClearPageHWPoison(p))
+				num_poisoned_pages_dec();
+			unlock_page(p);
+			put_page(p);
+			flags &= ~MF_COUNT_INCREASED;
+			retry = false;
+			goto try_again;
+		}
 		action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
 		res = -EBUSY;
 		goto unlock_page;