Re: [PATCH] mm: Fix THP handling in invalidate_mapping_pages()

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Mon, Jun 19, 2017 at 02:47:23PM +0200, Jan Kara wrote:
> The condition checking for THP straddling end of invalidated range is
> wrong - it checks 'index' against 'end' but 'index' has been already
> advanced to point to the end of THP and thus the condition can never be
> true. As a result THP straddling 'end' has been fully invalidated. Given
> the nature of invalidate_mapping_pages(), this could be only performance
> issue. In fact, we are lucky the condition is wrong because if it was
> ever true, we'd leave locked page behind.
> 
> Fix the condition checking for THP straddling 'end' and also properly
> unlock the page. Also update the comment before the condition to explain
> why we decide not to invalidate the page as it was not clear to me and I
> had to ask Kirill.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Thanks a lot for the fix.

-- 
 Kirill A. Shutemov

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