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

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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: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2025-04-30 10:59:30 +02:00
parent de6b4f9901
commit f049a4f7ff
1 changed files with 2 additions and 7 deletions
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9
arch/s390/mm/pgalloc.c
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@ -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);