mm/mmap: Remove preallocation from do_mas_align_munmap()

In preparation of passing the vma state through split, the
pre-allocation that occurs before the split has to be moved to after.
Since the preallocation would then live right next to the store, just
call store instead of preallocating.  This effectively restores the
potential error path of splitting and not munmap'ing which pre-dates the
maple tree.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

diff --git a/mm/mmap.c b/mm/mmap.c
index 560f66e4974971b51b2f2d3f66a2b556fe745f5e..fe200ac49f46baddd0f8737d23ac54f13a74f763 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2384,9 +2384,6 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
        mt_init_flags(&mt_detach, MT_FLAGS_LOCK_EXTERN);
        mt_set_external_lock(&mt_detach, &mm->mmap_lock);
 
-       if (mas_preallocate(mas, vma, GFP_KERNEL))
-               return -ENOMEM;
-
        mas->last = end - 1;
        /*
         * If we need to split any vma, do it now to save pain later.
@@ -2477,8 +2474,6 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
                        goto userfaultfd_error;
        }
 
-       /* Point of no return */
-       mas_set_range(mas, start, end - 1);
 #if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
        /* Make sure no VMAs are about to be lost. */
        {
@@ -2486,6 +2481,7 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
                struct vm_area_struct *vma_mas, *vma_test;
                int test_count = 0;
 
+               mas_set_range(mas, start, end - 1);
                rcu_read_lock();
                vma_test = mas_find(&test, end - 1);
                mas_for_each(mas, vma_mas, end - 1) {
@@ -2495,10 +2491,13 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
                }
                rcu_read_unlock();
                BUG_ON(count != test_count);
-               mas_set_range(mas, start, end - 1);
        }
 #endif
-       mas_store_prealloc(mas, NULL);
+       /* Point of no return */
+       mas_set_range(mas, start, end - 1);
+       if (mas_store_gfp(mas, NULL, GFP_KERNEL))
+               return -ENOMEM;
+
        mm->map_count -= count;
        /*
         * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
@@ -2530,7 +2529,6 @@ end_split_failed:
        __mt_destroy(&mt_detach);
 start_split_failed:
 map_count_exceeded:
-       mas_destroy(mas);
        return error;
 }