Allow hmm_range_fault() to return success (0) when the range has no access (!(vma->vm_flags & VM_READ)). The range->pfns[] array will be filled with range->values[HMM_PFN_NONE] in this case. This allows the caller to get a snapshot of a range without having to lookup the vma before calling hmm_range_fault(). If the call to hmm_range_fault() is not a snapshot, the caller can still check that pfns have the desired access permissions.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com Cc: "Jérôme Glisse" jglisse@redhat.com Cc: Jason Gunthorpe jgg@mellanox.com Cc: Christoph Hellwig hch@lst.de --- mm/hmm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/hmm.c b/mm/hmm.c index 7217912bef13..16c834e5d1c0 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -795,7 +795,9 @@ static int hmm_vma_walk_test(unsigned long start, */ if (!(vma->vm_flags & VM_READ)) { (void) hmm_pfns_fill(start, end, range, HMM_PFN_NONE); - return -EPERM; + + /* Skip this vma and continue processing the next vma. */ + return 1; }
return 0;