Commit 0adbd047 authored by Zi Yan's avatar Zi Yan Committed by Liu Shixin
Browse files

mm/migrate: correct nr_failed in migrate_pages_sync() 

mainline inclusion
from mainline-v6.7-rc1
commit a259945efe6ada94087ef666e9b38f8e34ea34ba
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9IP8P
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a259945efe6ada94087ef666e9b38f8e34ea34ba

--------------------------------

nr_failed was missing the large folio splits from migrate_pages_batch()
and can cause a mismatch between migrate_pages() return value and the
number of not migrated pages, i.e., when the return value of
migrate_pages() is 0, there are still pages left in the from page list.
It will happen when a non-PMD THP large folio fails to migrate due to
-ENOMEM and is split successfully but not all the split pages are not
migrated, migrate_pages_batch() would return non-zero, but
astats.nr_thp_split = 0.  nr_failed would be 0 and returned to the caller
of migrate_pages(), but the not migrated pages are left in the from page
list without being added back to LRU lists.

Fix it by adding a new nr_split counter for large folio splits and adding
it to nr_failed in migrate_page_sync() after migrate_pages_batch() is
done.

Link: https://lkml.kernel.org/r/20231017163129.2025214-1-zi.yan@sent.com


Fixes: 2ef7dbb2 ("migrate_pages: try migrate in batch asynchronously firstly")
Signed-off-by: default avatarZi Yan <ziy@nvidia.com>
Acked-by: default avatarHuang Ying <ying.huang@intel.com>
Reviewed-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 0c8d7c88

mm/migrate.c

+13 −3
Original line number Diff line number Diff line
@@ -1511,6 +1511,7 @@ struct migrate_pages_stats { 
	int nr_thp_succeeded;	/* THP migrated successfully */

	int nr_thp_failed;	/* THP failed to be migrated */

	int nr_thp_split;	/* THP split before migrating */

	int nr_split;	/* Large folio (include THP) split before migrating */

};



/*
@@ -1630,6 +1631,7 @@ static int migrate_pages_batch(struct list_head *from, 
	int nr_retry_pages = 0;

	int pass = 0;

	bool is_thp = false;

	bool is_large = false;

	struct folio *folio, *folio2, *dst = NULL, *dst2;

	int rc, rc_saved = 0, nr_pages;

	LIST_HEAD(unmap_folios);
@@ -1645,7 +1647,8 @@ static int migrate_pages_batch(struct list_head *from, 
		nr_retry_pages = 0;



		list_for_each_entry_safe(folio, folio2, from, lru) {

			is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio);

			is_large = folio_test_large(folio);

			is_thp = is_large && folio_test_pmd_mappable(folio);

			nr_pages = folio_nr_pages(folio);



			cond_resched();
@@ -1665,6 +1668,7 @@ static int migrate_pages_batch(struct list_head *from, 
				stats->nr_thp_failed++;

				if (!try_split_folio(folio, split_folios)) {

					stats->nr_thp_split++;

					stats->nr_split++;

					continue;

				}

				stats->nr_failed_pages += nr_pages;
@@ -1693,11 +1697,12 @@ static int migrate_pages_batch(struct list_head *from, 
				nr_failed++;

				stats->nr_thp_failed += is_thp;

				/* Large folio NUMA faulting doesn't split to retry. */

				if (folio_test_large(folio) && !nosplit) {

				if (is_large && !nosplit) {

					int ret = try_split_folio(folio, split_folios);



					if (!ret) {

						stats->nr_thp_split += is_thp;

						stats->nr_split += is_large;

						break;

					} else if (reason == MR_LONGTERM_PIN &&

						   ret == -EAGAIN) {
@@ -1843,6 +1848,7 @@ static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, 
	stats->nr_succeeded += astats.nr_succeeded;

	stats->nr_thp_succeeded += astats.nr_thp_succeeded;

	stats->nr_thp_split += astats.nr_thp_split;

	stats->nr_split += astats.nr_split;

	if (rc < 0) {

		stats->nr_failed_pages += astats.nr_failed_pages;

		stats->nr_thp_failed += astats.nr_thp_failed;
@@ -1850,7 +1856,11 @@ static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, 
		return rc;

	}

	stats->nr_thp_failed += astats.nr_thp_split;

	nr_failed += astats.nr_thp_split;

	/*

	 * Do not count rc, as pages will be retried below.

	 * Count nr_split only, since it includes nr_thp_split.

	 */

	nr_failed += astats.nr_split;

	/*

	 * Fall back to migrate all failed folios one by one synchronously. All

	 * failed folios except split THPs will be retried, so their failure