Re: [PATCH] thp: Fix deadlock situation in vma_adjust with huge page in page cache.

[Ning Qu <quning@google.com>]

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Oh, sorry about that. Let me see what's going on here.

Best wishes,
-- 
Ning Qu (曲宁) | Software Engineer | quning@google.com | +1-408-418-6066


On Fri, Aug 9, 2013 at 2:34 PM, Ning Qu <quning@google.com> wrote:

> In vma_adjust, the current code grabs i_mmap_mutex before calling
> vma_adjust_trans_huge. This used to be fine until huge page in page
> cache comes in. The problem is the underlying function
> split_file_huge_page will also grab the i_mmap_mutex before splitting
> the huge page in page cache. Obviously this is causing deadlock
> situation.
>
> This fix is to move the vma_adjust_trans_huge before grab the lock for
> file, the same as what the function is currently doing for anonymous
> memory. Tested, everything works fine so far.
>
> Signed-off-by: Ning Qu <quning@google.com>
> ---
>  mm/mmap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 519ce78..accf1b3 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -750,6 +750,8 @@ again: remove_next = 1 + (end > next->vm_end);
>   }
>   }
>
> + vma_adjust_trans_huge(vma, start, end, adjust_next);
> +
>   if (file) {
>   mapping = file->f_mapping;
>   if (!(vma->vm_flags & VM_NONLINEAR)) {
> @@ -773,8 +775,6 @@ again: remove_next = 1 + (end > next->vm_end);
>   }
>   }
>
> - vma_adjust_trans_huge(vma, start, end, adjust_next);
> -
>   anon_vma = vma->anon_vma;
>   if (!anon_vma && adjust_next)
>   anon_vma = next->anon_vma;
> --
> 1.8.3
>

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