s390: Fix runtime warning about negative pgtables_bytes

groeck · Martin Schwidefsky · commit 61e18270f604 · 2018-03-02T12:48:40.000+01:00
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 b4e98d9 ("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: b4e98d9 ("mm: account pud page tables") Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
@@ -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;

Original file line number	Diff line number	Diff line change
`@@ -63,6 +63,7 @@ static inline int init_new_context(struct task_struct *tsk,`
`63`	`63`	`_ASCE_USER_BITS \| _ASCE_TYPE_SEGMENT;`
`64`	`64`	`/* pgd_alloc() did not account this pmd */`
`65`	`65`	`mm_inc_nr_pmds(mm);`
	`66`	`+ mm_inc_nr_puds(mm);`
`66`	`67`	`}`
`67`	`68`	`crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));`
`68`	`69`	`return 0;`