2021-07-27 03:41:08

by 王擎

Subject: [PATCH] mm: folio: use copy_highpage() instead of folio_migrate_copy() when copy once

folio_migrate_copy() will call cond_resched(), even if it only needs to be
copied once, restore the previous implementation before there is a better
solution: use copy_highpage() when copy once.

Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
___might_sleep.cold+0x1f3/0x239 kernel/sched/core.c:9182
folio_copy+0x10c/0x1a0 mm/util.c:761
folio_migrate_copy+0x19/0x30 mm/migrate.c:619
__buffer_migrate_page+0x820/0xa80 mm/migrate.c:757
move_to_new_page+0x339/0xf00 mm/migrate.c:904
__unmap_and_move mm/migrate.c:1069 [inline]
unmap_and_move mm/migrate.c:1210 [inline]
migrate_pages+0x2867/0x3890 mm/migrate.c:1487
compact_zone+0x1abb/0x3860 mm/compaction.c:2393
kcompactd_do_work+0x2c9/0x730 mm/compaction.c:2808
kcompactd+0x262/0xd10 mm/compaction.c:2903
kthread+0x3e5/0x4d0 kernel/kthread.c:319

Reported-by: [email protected]
Signed-off-by: Wang Qing <[email protected]>
---
mm/folio-compat.c | 6 ------
mm/migrate.c | 15 +++++++++++----
2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 5b6ae1d..13ec6aa
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -64,12 +64,6 @@ void migrate_page_states(struct page *newpage, struct page *page)
folio_migrate_flags(page_folio(newpage), page_folio(page));
}
EXPORT_SYMBOL(migrate_page_states);
-
-void migrate_page_copy(struct page *newpage, struct page *page)
-{
- folio_migrate_copy(page_folio(newpage), page_folio(page));
-}
-EXPORT_SYMBOL(migrate_page_copy);
#endif

bool set_page_writeback(struct page *page)
diff --git a/mm/migrate.c b/mm/migrate.c
index 7d06515..8fb796b
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -614,12 +614,19 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
}
EXPORT_SYMBOL(folio_migrate_flags);

-void folio_migrate_copy(struct folio *newfolio, struct folio *folio)
+void migrate_page_copy(struct page *newpage, struct page *page)
{
- folio_copy(newfolio, folio);
+ struct folio *newfolio = page_folio(newpage);
+ struct folio *folio = page_folio(page);
+
+ if (PageHuge(page) || PageTransHuge(page))
+ folio_copy(newfolio, folio);
+ else
+ copy_highpage(newpage, page);
+
folio_migrate_flags(newfolio, folio);
}
-EXPORT_SYMBOL(folio_migrate_copy);
+EXPORT_SYMBOL(migrate_page_copy);

/************************************************************
* Migration functions
@@ -647,7 +654,7 @@ int migrate_page(struct address_space *mapping,
return rc;

if (mode != MIGRATE_SYNC_NO_COPY)
- folio_migrate_copy(newfolio, folio);
+ migrate_page_copy(newpage, page);
else
folio_migrate_flags(newfolio, folio);
return MIGRATEPAGE_SUCCESS;
--
2.7.4

2021-07-27 11:50:30

by Matthew Wilcox

Subject: Re: [PATCH] mm: folio: use copy_highpage() instead of folio_migrate_copy() when copy once

On Tue, Jul 27, 2021 at 11:32:54AM +0800, Wang Qing wrote:
> folio_migrate_copy() will call cond_resched(), even if it only needs to be
> copied once, restore the previous implementation before there is a better
> solution: use copy_highpage() when copy once.

no. i already fixed this on july 22.

https://lore.kernel.org/linux-mm/YPmB60EwQPpEvdb%[email protected]/