On Tue, Jan 03, 2023 at 06:16:36PM +0100, Jann Horn wrote:
On Tue, Jan 3, 2023 at 6:14 PM Jann Horn jannh@google.com wrote:
Since commit 70cbc3cc78a99 ("mm: gup: fix the fast GUP race against THP collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to ensure that the page table was not removed by khugepaged in between.
However, lockless_pages_from_mm() still requires that the page table is not concurrently freed. Fix it by sending IPIs (if the architecture uses semi-RCU-style page table freeing) before freeing/reusing page tables.
Link: https://lkml.kernel.org/r/20221129154730.2274278-2-jannh@google.com Link: https://lkml.kernel.org/r/20221128180252.1684965-2-jannh@google.com Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com Fixes: ba76149f47d8 ("thp: khugepaged") Signed-off-by: Jann Horn jannh@google.com Reviewed-by: Yang Shi shy828301@gmail.com Acked-by: David Hildenbrand david@redhat.com Cc: John Hubbard jhubbard@nvidia.com Cc: Peter Xu peterx@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org [manual backport: two of the three places in khugepaged that can free ptes were refactored into a common helper between 5.15 and 6.0; TLB flushing was refactored between 5.4 and 5.10; TLB flushing was refactored between 4.19 and 5.4; pmd collapse for PTE-mapped THP was only added in 5.4; ugly hack for s390 and arm in <=4.19]
Or if you just want a fixup commit, you can add this to 4.9, 4.14 and 4.19:
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0f217bb9b534..0a4cace1cfc4 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -24,7 +24,7 @@ #include "internal.h"
/* gross hack for <=4.19 stable */ -#ifdef CONFIG_S390 +#if defined(CONFIG_S390) || defined(CONFIG_ARM) static void tlb_remove_table_smp_sync(void *arg) { /* Simply deliver the interrupt */
Let me know if you want me to send a fixup instead, since the broken-on-arm version of this patch is already in a stable RC...
This works, now all fixed up in all 3 queues, thanks!
greg k-h