tree ea375fb462731dce8200eef3b650cd9acab2f1dd
parent e36acfe6c86d13eec62321e1e86a1ce287e52e7d
author Jason Gunthorpe <jgg@mellanox.com> 1558618606 -0300
committer Jason Gunthorpe <jgg@mellanox.com> 1560172233 -0300

mm/hmm: Hold a mmgrab from hmm to mm

So long as a struct hmm pointer exists, so should the struct mm it is
linked too. Hold the mmgrab() as soon as a hmm is created, and mmdrop() it
once the hmm refcount goes to zero.

Since mmdrop() (ie a 0 kref on struct mm) is now impossible with a !NULL
mm->hmm delete the hmm_hmm_destroy().

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Philip Yang <Philip.Yang@amd.com>