mm/hmm: do not erase snapshot when a range is invalidated

Users of HMM might be using the snapshot information to do preparatory
step like dma mapping pages to a device before checking for invalidation
through hmm_vma_range_done() so do not erase that information and assume
users will do the right thing.

Link: http://lkml.kernel.org/r/20190403193318.16478-4-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hmm.c b/mm/hmm.c
index 919d78fd21c55dad3d69a2a1a55d9399eebfe415..84e0577a912a724da2d9ce90477753f6e260f592 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -174,16 +174,10 @@ static int hmm_invalidate_range(struct hmm *hmm, bool device,
 
        spin_lock(&hmm->lock);
        list_for_each_entry(range, &hmm->ranges, list) {
-               unsigned long addr, idx, npages;
-
                if (update->end < range->start || update->start >= range->end)
                        continue;
 
                range->valid = false;
-               addr = max(update->start, range->start);
-               idx = (addr - range->start) >> PAGE_SHIFT;
-               npages = (min(range->end, update->end) - addr) >> PAGE_SHIFT;
-               memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
        }
        spin_unlock(&hmm->lock);