On Fri 03-11-17 10:05:51, Heiko Carstens wrote: > With "mm: account pud page tables" and "mm: consolidate page table > accounting" pud page table accounting was introduced which now results > in tons of warnings like this one on s390: > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > Reason for this are our run-time folded page tables: by default new > processes start with three page table levels where the allocated pgd > is the same as the first pud. In this case there won't ever be a pud > allocated and therefore mm_inc_nr_puds() will also never be called. > > However when freeing the address space free_pud_range() will call > exactly once mm_dec_nr_puds() which leads to misaccounting. > > Therefore call mm_inc_nr_puds() within init_new_context() to fix > this. This is the same like we have it already for processes that run > with two page table levels (aka compat processes). > > While at it also adjust the comment, since there is no "mm->nr_pmds" > anymore.
Subtle... Thanks for the fix, I didn't have any idea about this when reviewing. > Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com> > Cc: Michal Hocko <mho...@suse.com> > Cc: Gerald Schaefer <gerald.schae...@de.ibm.com> > Cc: Martin Schwidefsky <schwidef...@de.ibm.com> > Signed-off-by: Heiko Carstens <heiko.carst...@de.ibm.com> > --- > arch/s390/include/asm/mmu_context.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/s390/include/asm/mmu_context.h > b/arch/s390/include/asm/mmu_context.h > index 3c9abedc323c..4f943d58cbac 100644 > --- a/arch/s390/include/asm/mmu_context.h > +++ b/arch/s390/include/asm/mmu_context.h > @@ -43,6 +43,8 @@ static inline int init_new_context(struct task_struct *tsk, > mm->context.asce_limit = STACK_TOP_MAX; > mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | > _ASCE_USER_BITS | _ASCE_TYPE_REGION3; > + /* pgd_alloc() did not account this pud */ > + mm_inc_nr_puds(mm); > break; > case -PAGE_SIZE: > /* forked 5-level task, set new asce with new_mm->pgd */ > @@ -58,7 +60,7 @@ static inline int init_new_context(struct task_struct *tsk, > /* forked 2-level compat task, set new asce with new mm->pgd */ > mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | > _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; > - /* pgd_alloc() did not increase mm->nr_pmds */ > + /* pgd_alloc() did not account this pmd */ > mm_inc_nr_pmds(mm); > } > crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm)); > -- > 2.13.5 > -- Michal Hocko SUSE Labs
