Commit 28c5609f authored by Liam Howlett's avatar Liam Howlett Committed by Andrew Morton
Browse files

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: 2e7ce7d3 (mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap())
Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: default avatarYu Zhao <yuzhao@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7be1c1a3

mm/mmap.c

+6 −12
Original line number Diff line number Diff line
@@ -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 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma, 
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)