diff mbox series

[3/4] mm/hmm: allow hmm_range_fault() of mmap(PROT_NONE)

Message ID 20190911222829.28874-4-rcampbell@nvidia.com (mailing list archive)
State New, archived
Headers show
Series HMM tests and minor fixes | expand

Commit Message

Ralph Campbell Sept. 11, 2019, 10:28 p.m. UTC 
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 mbox series

Patch

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;