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authorandrew.yang <andrew.yang@mediatek.com>2022-03-22 14:46:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 15:57:09 -0700
commit356ea3865687926e5da7579d1f3351d3f0a322a1 (patch)
treee5f2593aa9013ea269204b789fb3a8fd5bf625d7 /mm/migrate.c
parentfc89213a636c3735eb3386f10a34c082271b4192 (diff)
mm/migrate: fix race between lock page and clear PG_Isolated
When memory is tight, system may start to compact memory for large continuous memory demands. If one process tries to lock a memory page that is being locked and isolated for compaction, it may wait a long time or even forever. This is because compaction will perform non-atomic PG_Isolated clear while holding page lock, this may overwrite PG_waiters set by the process that can't obtain the page lock and add itself to the waiting queue to wait for the lock to be unlocked. CPU1 CPU2 lock_page(page); (successful) lock_page(); (failed) __ClearPageIsolated(page); SetPageWaiters(page) (may be overwritten) unlock_page(page); The solution is to not perform non-atomic operation on page flags while holding page lock. Link: https://lkml.kernel.org/r/20220315030515.20263-1-andrew.yang@mediatek.com Signed-off-by: andrew.yang <andrew.yang@mediatek.com> Cc: Matthias Brugger <matthias.bgg@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: "Vlastimil Babka" <vbabka@suse.cz> Cc: David Howells <dhowells@redhat.com> Cc: "William Kucharski" <william.kucharski@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Nicholas Tang <nicholas.tang@mediatek.com> Cc: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r--mm/migrate.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 67616ee4aa26..c0d16f050fec 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -107,7 +107,7 @@ int isolate_movable_page(struct page *page, isolate_mode_t mode)
/* Driver shouldn't use PG_isolated bit of page->flags */
WARN_ON_ONCE(PageIsolated(page));
- __SetPageIsolated(page);
+ SetPageIsolated(page);
unlock_page(page);
return 0;
@@ -126,7 +126,7 @@ static void putback_movable_page(struct page *page)
mapping = page_mapping(page);
mapping->a_ops->putback_page(page);
- __ClearPageIsolated(page);
+ ClearPageIsolated(page);
}
/*
@@ -159,7 +159,7 @@ void putback_movable_pages(struct list_head *l)
if (PageMovable(page))
putback_movable_page(page);
else
- __ClearPageIsolated(page);
+ ClearPageIsolated(page);
unlock_page(page);
put_page(page);
} else {
@@ -883,7 +883,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
VM_BUG_ON_PAGE(!PageIsolated(page), page);
if (!PageMovable(page)) {
rc = MIGRATEPAGE_SUCCESS;
- __ClearPageIsolated(page);
+ ClearPageIsolated(page);
goto out;
}
@@ -905,7 +905,7 @@ static int move_to_new_page(struct page *newpage, struct page *page,
* We clear PG_movable under page_lock so any compactor
* cannot try to migrate this page.
*/
- __ClearPageIsolated(page);
+ ClearPageIsolated(page);
}
/*
@@ -1091,7 +1091,7 @@ static int unmap_and_move(new_page_t get_new_page,
if (unlikely(__PageMovable(page))) {
lock_page(page);
if (!PageMovable(page))
- __ClearPageIsolated(page);
+ ClearPageIsolated(page);
unlock_page(page);
}
goto out;