I'm glad to see this series back, and nicely presented: thank you.
Not worth respinning them, but consider 1,2,3,4,5,6,7 and 9 as
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
On Thu, 30 Oct 2014, Davidlohr Bueso wrote:
> As per the comment in move_ptes(), we only require taking the
> anon vma and i_mmap locks to ensure that rmap will always observe
> either the old or new ptes, in the case of need_rmap_lock=true.
> No modifications to the tree itself, thus share the i_mmap_rwsem.
>
> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
But this one is Nacked by me. I don't understand how you and Kirill
could read Michel's painstaking comment on need_rmap_locks, then go
go ahead and remove the exclusion of rmap_walk().
I agree the code here does not modify the interval tree, but the
comment explains how we're moving a pte from one place in the tree
to another, and in some cases there's a danger that the rmap walk
might miss the pte from both places (which doesn't matter much to
most of its uses, but is critical in page migration).
Or am I the one missing something?
Hugh
> ---
> mm/mremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index c929324..09bd644 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -119,7 +119,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
> if (need_rmap_locks) {
> if (vma->vm_file) {
> mapping = vma->vm_file->f_mapping;
> - i_mmap_lock_write(mapping);
> + i_mmap_lock_read(mapping);
> }
> if (vma->anon_vma) {
> anon_vma = vma->anon_vma;
> @@ -156,7 +156,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
> if (anon_vma)
> anon_vma_unlock_read(anon_vma);
> if (mapping)
> - i_mmap_unlock_write(mapping);
> + i_mmap_unlock_read(mapping);
> }
>
> #define LATENCY_LIMIT (64 * PAGE_SIZE)
> --
> 1.8.4.5
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