Commit f049a4f7 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/mm: Add mmap_assert_write_locked() check to crst_table_upgrade() 



Add mmap_assert_write_locked() check to crst_table_upgrade() in order to
verify that no concurrent page table upgrades of an mm can happen. This
allows to remove the VM_BUG_ON() check which checks for the potential
inconsistent result of concurrent updates.

Reviewed-by: default avatarGerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent de6b4f99

arch/s390/mm/pgalloc.c

+2 −7
Original line number Diff line number Diff line
@@ -56,6 +56,8 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end) 
	unsigned long *pgd = NULL, *p4d = NULL, *__pgd;

	unsigned long asce_limit = mm->context.asce_limit;



	mmap_assert_write_locked(mm);



	/* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */

	VM_BUG_ON(asce_limit < _REGION2_SIZE);
@@ -79,13 +81,6 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end) 


	spin_lock_bh(&mm->page_table_lock);



	/*

	 * This routine gets called with mmap_lock lock held and there is

	 * no reason to optimize for the case of otherwise. However, if

	 * that would ever change, the below check will let us know.

	 */

	VM_BUG_ON(asce_limit != mm->context.asce_limit);



	if (p4d) {

		__pgd = (unsigned long *) mm->pgd;

		p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);