From 0d8a83644b26f61c4120e63512aba979ac04f320 Mon Sep 17 00:00:00 2001 From: "andrew.yang" Date: Tue, 15 Mar 2022 16:58:34 +1100 Subject: [PATCH] FROMGIT: 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 Cc: Matthias Brugger Cc: Matthew Wilcox Cc: "Vlastimil Babka" Cc: David Howells Cc: "William Kucharski" Cc: David Hildenbrand Cc: Yang Shi Cc: Marc Zyngier Cc: Nicholas Tang Cc: Kuan-Ying Lee Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell (cherry picked from commit 48911e41ddee4fe113bf1e4303dda1a413b169c9 https://github.com/hnaz/linux-mm.git) Bug: 225086204 Change-Id: I3dc59bf75f12d4ee93779bcbe9336c6376d2d6b6 --- include/linux/page-flags.h | 2 +- mm/migrate.c | 12 ++++++------ 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index fbfd3fad48f2..624ae3846758 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -791,7 +791,7 @@ PAGE_TYPE_OPS(Guard, guard) extern bool is_free_buddy_page(struct page *page); -__PAGEFLAG(Isolated, isolated, PF_ANY); +PAGEFLAG(Isolated, isolated, PF_ANY); /* * If network-based swap is enabled, sl*b must keep track of whether pages diff --git a/mm/migrate.c b/mm/migrate.c index c5974fff3395..f1401363bea6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -106,7 +106,7 @@ 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; @@ -125,7 +125,7 @@ static void putback_movable_page(struct page *page) mapping = page_mapping(page); mapping->a_ops->putback_page(page); - __ClearPageIsolated(page); + ClearPageIsolated(page); } /* @@ -158,7 +158,7 @@ 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 { @@ -916,7 +916,7 @@ 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; } @@ -938,7 +938,7 @@ 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); } /* @@ -1199,7 +1199,7 @@ 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;