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s390: Fix runtime warning about negative pgtables_bytes 

When running s390 images with 'compat' processes, the following
BUG is seen repeatedly.

BUG: non-zero pgtables_bytes on freeing mm: -16384

Bisect points to commit b4e98d9ac7 ("mm: account pud page tables").
Analysis shows that init_new_context() is called with
mm->context.asce_limit set to _REGION3_SIZE. In this situation,
pgtables_bytes remains set to 0 and is not increased. The message is
displayed when the affected process dies and mm_dec_nr_puds() is called.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Fixes: b4e98d9ac7 ("mm: account pud page tables")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Guenter Roeck 2018-03-01 14:40:52 -08:00 committed by Martin Schwidefsky
parent d5feec04fe
commit 61e18270f6
1 changed files with 1 additions and 0 deletions
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1
arch/s390/include/asm/mmu_context.h
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@ -63,6 +63,7 @@ static inline int init_new_context(struct task_struct *tsk,
_ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
/* pgd_alloc() did not account this pmd */
mm_inc_nr_pmds(mm);
mm_inc_nr_puds(mm);
}
crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
return 0;