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mm/migrate: correct nr_failed in migrate_pages_sync() 

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: 2ef7dbb269 ("migrate_pages: try migrate in batch asynchronously firstly")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zi Yan 2023-10-17 12:31:28 -04:00 committed by Andrew Morton
parent 245245c2ff
commit a259945efe
1 changed files with 13 additions and 3 deletions
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16
mm/migrate.c
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@ -1495,6 +1495,7 @@ 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 */
};
/*
@ -1614,6 +1615,7 @@ 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);
@ -1629,7 +1631,8 @@ 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();
@ -1649,6 +1652,7 @@ 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;
@ -1677,11 +1681,12 @@ 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) {
@ -1827,6 +1832,7 @@ 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;
@ -1834,7 +1840,11 @@ 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