The patch titled Subject: mm/migrate: correct nr_failed in migrate_pages_sync() has been added to the -mm mm-unstable branch. Its filename is mm-migrate-correct-nr_failed-in-migrate_pages_sync.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate-correct-nr_failed-in-migrate_pages_sync.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Zi Yan <ziy@xxxxxxxxxx> Subject: mm/migrate: correct nr_failed in migrate_pages_sync() Date: Mon, 16 Oct 2023 11:41:56 -0400 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 =3D 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/20231016154156.1948815-1-zi.yan@xxxxxxxx Fixes: 2ef7dbb26990 ("migrate_pages: try migrate in batch asynchronously fi= rstly") Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/trace/events/migrate.h | 24 ++++++++++++++---------- mm/migrate.c | 15 +++++++++++---- 2 files changed, 25 insertions(+), 14 deletions(-) --- a/include/trace/events/migrate.h~mm-migrate-correct-nr_failed-in-migrate_pages_sync +++ a/include/trace/events/migrate.h @@ -49,10 +49,11 @@ TRACE_EVENT(mm_migrate_pages, TP_PROTO(unsigned long succeeded, unsigned long failed, unsigned long thp_succeeded, unsigned long thp_failed, - unsigned long thp_split, enum migrate_mode mode, int reason), + unsigned long thp_split, unsigned long large_folio_split, + enum migrate_mode mode, int reason), TP_ARGS(succeeded, failed, thp_succeeded, thp_failed, - thp_split, mode, reason), + thp_split, large_folio_split, mode, reason), TP_STRUCT__entry( __field( unsigned long, succeeded) @@ -60,26 +61,29 @@ TRACE_EVENT(mm_migrate_pages, __field( unsigned long, thp_succeeded) __field( unsigned long, thp_failed) __field( unsigned long, thp_split) + __field( unsigned long, large_folio_split) __field( enum migrate_mode, mode) __field( int, reason) ), TP_fast_assign( - __entry->succeeded = succeeded; - __entry->failed = failed; - __entry->thp_succeeded = thp_succeeded; - __entry->thp_failed = thp_failed; - __entry->thp_split = thp_split; - __entry->mode = mode; - __entry->reason = reason; + __entry->succeeded = succeeded; + __entry->failed = failed; + __entry->thp_succeeded = thp_succeeded; + __entry->thp_failed = thp_failed; + __entry->thp_split = thp_split; + __entry->large_folio_split = large_folio_split; + __entry->mode = mode; + __entry->reason = reason; ), - TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu mode=%s reason=%s", + TP_printk("nr_succeeded=%lu nr_failed=%lu nr_thp_succeeded=%lu nr_thp_failed=%lu nr_thp_split=%lu nr_split=%lu mode=%s reason=%s", __entry->succeeded, __entry->failed, __entry->thp_succeeded, __entry->thp_failed, __entry->thp_split, + __entry->large_folio_split, __print_symbolic(__entry->mode, MIGRATE_MODE), __print_symbolic(__entry->reason, MIGRATE_REASON)) ); --- a/mm/migrate.c~mm-migrate-correct-nr_failed-in-migrate_pages_sync +++ a/mm/migrate.c @@ -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 li 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 li 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 li 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 li 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++; break; } else if (reason == MR_LONGTERM_PIN && ret == -EAGAIN) { @@ -1827,6 +1832,7 @@ static int migrate_pages_sync(struct lis 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 +1840,7 @@ static int migrate_pages_sync(struct lis return rc; } stats->nr_thp_failed += astats.nr_thp_split; - nr_failed += astats.nr_thp_split; + nr_failed += astats.nr_split + astats.nr_thp_split; /* * Fall back to migrate all failed folios one by one synchronously. All * failed folios except split THPs will be retried, so their failure @@ -1969,7 +1975,8 @@ out: count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split); trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages, stats.nr_thp_succeeded, stats.nr_thp_failed, - stats.nr_thp_split, mode, reason); + stats.nr_thp_split, stats.nr_split, mode, + reason); if (ret_succeeded) *ret_succeeded = stats.nr_succeeded; _ Patches currently in -mm which might be from ziy@xxxxxxxxxx are mm-migrate-correct-nr_failed-in-migrate_pages_sync.patch