mm/hmm: Use hmm_mirror not mm as an argument for hmm_range_register
Ralph observes that hmm_range_register() can only be called by a driver
while a mirror is registered. Make this clear in the API by passing in the
mirror structure as a parameter.
This also simplifies understanding the lifetime model for struct hmm, as
the hmm pointer must be valid as part of a registered mirror so all we
need in hmm_register_range() is a simple kref_get.
Suggested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.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>
diff --git a/mm/hmm.c b/mm/hmm.c
index f6956d7..22a97ad 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -914,13 +914,13 @@ static void hmm_pfns_clear(struct hmm_range *range,
* Track updates to the CPU page table see include/linux/hmm.h
*/
int hmm_range_register(struct hmm_range *range,
- struct mm_struct *mm,
+ struct hmm_mirror *mirror,
unsigned long start,
unsigned long end,
unsigned page_shift)
{
unsigned long mask = ((1UL << page_shift) - 1UL);
- struct hmm *hmm;
+ struct hmm *hmm = mirror->hmm;
range->valid = false;
range->hmm = NULL;
@@ -934,20 +934,15 @@ int hmm_range_register(struct hmm_range *range,
range->start = start;
range->end = end;
- hmm = hmm_get_or_create(mm);
- if (!hmm)
- return -EFAULT;
-
/* Check if hmm_mm_destroy() was call. */
- if (hmm->mm == NULL || hmm->dead) {
- hmm_put(hmm);
+ if (hmm->mm == NULL || hmm->dead)
return -EFAULT;
- }
/* Initialize range to track CPU page table updates. */
mutex_lock(&hmm->lock);
range->hmm = hmm;
+ kref_get(&hmm->kref);
list_add_rcu(&range->list, &hmm->ranges);
/*
