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>

1 files changed, 13 insertions, 8 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 94f37a9fb1e5..a9be08899b0c 100644
--- 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;