s390/mm: page_table_realloc returns failure

There is a possible race between setting has_pgste and reallocation of the
page_table, change the order to fix this.
Also page_table_alloc_pgste can fail, in that case we need to backpropagte this
as -ENOMEM to the caller of page_table_realloc.

Based on a patch by Christian Borntraeger <borntraeger@de.ibm.com>.

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 94f37a9fb1e543d2abc1efc318aa80212ae6db13..a9be08899b0c7a1153974cb5146079077811547e 100644 (file)
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1087,10 +1087,9 @@ again:
                        continue;
                /* Allocate new page table with pgstes */
                new = page_table_alloc_pgste(mm, addr);
-               if (!new) {
-                       mm->context.has_pgste = 0;
-                       continue;
-               }
+               if (!new)
+                       return -ENOMEM;
+
                spin_lock(&mm->page_table_lock);
                if (likely((unsigned long *) pmd_deref(*pmd) == table)) {
                        /* Nuke pmd entry pointing to the "short" page table */
@@ -1128,13 +1127,15 @@ static unsigned long page_table_realloc_pud(struct mmu_gather *tlb,
                if (pud_none_or_clear_bad(pud))
                        continue;
                next = page_table_realloc_pmd(tlb, mm, pud, addr, next);
+               if (unlikely(IS_ERR_VALUE(next)))
+                       return next;
        } while (pud++, addr = next, addr != end);
 
        return addr;
 }
 
-static void page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
-                              unsigned long addr, unsigned long end)
+static unsigned long page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
+                                       unsigned long addr, unsigned long end)
 {
        unsigned long next;
        pgd_t *pgd;
@@ -1145,7 +1146,11 @@ static void page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
                if (pgd_none_or_clear_bad(pgd))
                        continue;
                next = page_table_realloc_pud(tlb, mm, pgd, addr, next);
+               if (unlikely(IS_ERR_VALUE(next)))
+                       return next;
        } while (pgd++, addr = next, addr != end);
+
+       return 0;
 }
 
 /*
@@ -1165,9 +1170,9 @@ int s390_enable_sie(void)
        /* split thp mappings and disable thp for future mappings */
        thp_split_mm(mm);
        /* Reallocate the page tables with pgstes */
-       mm->context.has_pgste = 1;
        tlb_gather_mmu(&tlb, mm, 0, TASK_SIZE);
-       page_table_realloc(&tlb, mm, 0, TASK_SIZE);
+       if (!page_table_realloc(&tlb, mm, 0, TASK_SIZE))
+               mm->context.has_pgste = 1;
        tlb_finish_mmu(&tlb, 0, TASK_SIZE);
        up_write(&mm->mmap_sem);
        return mm->context.has_pgste ? 0 : -ENOMEM;