Re: [PATCH v2 6/9] hugetlb: add vma based lock for pmd sharing

[Mike Kravetz]

On 09/14/22 15:18, Mike Kravetz wrote:
> Allocate a new hugetlb_vma_lock structure and hang off vm_private_data
> for synchronization use by vmas that could be involved in pmd sharing.
> This data structure contains a rw semaphore that is the primary tool
> used for synchronization.
> 
> This new structure is ref counted, so that it can exist when NOT attached
> to a vma.  This is only helpful in resolving lock ordering issues where
> code may need to obtain the vma_lock while there are no guarantees the
> vma may go away.  By obtaining a ref on the structure, it can be
> guaranteed that at least the rw semaphore will not go away.
> 
> Only add infrastructure for the new lock here.  Actual use will be added
> in subsequent patches.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
>  include/linux/hugetlb.h |  43 ++++++++-
>  kernel/fork.c           |   6 +-
>  mm/hugetlb.c            | 202 ++++++++++++++++++++++++++++++++++++----
>  mm/rmap.c               |   8 +-
>  4 files changed, 235 insertions(+), 24 deletions(-)

Reviewers - FYI, the following was added to address a build issue caused
by this patch.