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Date: Wed, 12 Oct 2016 20:33:57 +0800 From: lizf@...nel.org To: stable@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Zefan Li <lizefan@...wei.com> Subject: [PATCH 3.4 121/125] Fix incomplete backport of commit 0f792cf949a0 From: Zefan Li <lizefan@...wei.com> 3.4.113-rc1 review patch. If anyone has any objections, please let me know. ------------------ Signed-off-by: Zefan Li <lizefan@...wei.com> --- mm/hugetlb.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 416cbfd..6726bfe 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2929,13 +2929,17 @@ out_page_table_lock: unlock_page(pagecache_page); put_page(pagecache_page); } - if (page != pagecache_page) - unlock_page(page); - put_page(page); - out_mutex: mutex_unlock(&hugetlb_instantiation_mutex); - + /* + * Generally it's safe to hold refcount during waiting page lock. But + * here we just wait to defer the next page fault to avoid busy loop and + * the page is not used after unlocked before returning from the current + * page fault. So we are safe from accessing freed page, even if we wait + * here without taking refcount. + */ + if (need_wait_lock) + wait_on_page_locked(page); return ret; } -- 1.9.1
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