From: Oscar Salvador <osalvador@xxxxxxx> Subject: mm,hwpoison: try to narrow window race for free pages Aristeu Rozanski reported that a customer test case started to report -EBUSY after the hwpoison rework patchset. There is a race window between spotting a free page and taking it off its buddy freelist, so it might be that by the time we try to take it off, the page has been already allocated. This patch tries to handle such race window by trying to handle the new type of page again if the page was allocated under us. Link: https://lkml.kernel.org/r/20200922135650.1634-15-osalvador@xxxxxxx Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> Reported-by: Aristeu Rozanski <aris@xxxxxxxxx> Tested-by: Aristeu Rozanski <aris@xxxxxxxxx> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Dmitry Yakunin <zeil@xxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory-failure.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/mm/memory-failure.c~mmhwpoison-try-to-narrow-window-race-for-free-pages +++ a/mm/memory-failure.c @@ -1903,6 +1903,7 @@ int soft_offline_page(unsigned long pfn, { int ret; struct page *page; + bool try_again = true; if (!pfn_valid(pfn)) return -ENXIO; @@ -1918,6 +1919,7 @@ int soft_offline_page(unsigned long pfn, return 0; } +retry: get_online_mems(); ret = get_any_page(page, pfn, flags); put_online_mems(); @@ -1925,7 +1927,10 @@ int soft_offline_page(unsigned long pfn, if (ret > 0) ret = soft_offline_in_use_page(page); else if (ret == 0) - ret = soft_offline_free_page(page); + if (soft_offline_free_page(page) && try_again) { + try_again = false; + goto retry; + } return ret; } _
