mm/mmap: preallocate maple nodes for brk vma expansion

If the brk VMA is the last vma in a maple node and meets the rare criteria
that it can be expanded, then preallocation is necessary to avoid a
potential fs_reclaim circular lock issue on low resources.

At the same time use the actual vma start address (unaligned) when calling
vma_adjust_trans_huge().

Link: https://lkml.kernel.org/r/20221011160624.1253454-1-Liam.Howlett@oracle.com
Fixes: 2e7ce7d354f2 (mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap())
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index fc8581c..5855f26 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2942,17 +2942,18 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
        if (vma &&
            (!vma->anon_vma || list_is_singular(&vma->anon_vma_chain)) &&
            ((vma->vm_flags & ~VM_SOFTDIRTY) == flags)) {
-               mas->index = vma->vm_start;
-               mas->last = addr + len - 1;
-               vma_adjust_trans_huge(vma, addr, addr + len, 0);
+               mas_set_range(mas, vma->vm_start, addr + len - 1);
+               if (mas_preallocate(mas, vma, GFP_KERNEL))
+                       return -ENOMEM;
+
+               vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
                if (vma->anon_vma) {
                        anon_vma_lock_write(vma->anon_vma);
                        anon_vma_interval_tree_pre_update_vma(vma);
                }
                vma->vm_end = addr + len;
                vma->vm_flags |= VM_SOFTDIRTY;
-               if (mas_store_gfp(mas, vma, GFP_KERNEL))
-                       goto mas_expand_failed;
+               mas_store_prealloc(mas, vma);
 
                if (vma->anon_vma) {
                        anon_vma_interval_tree_post_update_vma(vma);
@@ -2993,13 +2994,6 @@ mas_store_fail:
 vma_alloc_fail:
        vm_unacct_memory(len >> PAGE_SHIFT);
        return -ENOMEM;
-
-mas_expand_failed:
-       if (vma->anon_vma) {
-               anon_vma_interval_tree_post_update_vma(vma);
-               anon_vma_unlock_write(vma->anon_vma);
-       }
-       return -ENOMEM;
 }
 
 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)