[PATCH 02/10] mm/hmm: do not erase snapshot when a range is invalidated

From: jglisse@redhat.com
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	"John Hubbard" <jhubbard@nvidia.com>
Subject: [PATCH 02/10] mm/hmm: do not erase snapshot when a range is invalidated
Date: Tue, 29 Jan 2019 11:54:20 -0500	[thread overview]
Message-ID: <20190129165428.3931-3-jglisse@redhat.com> (raw)
In-Reply-To: <20190129165428.3931-1-jglisse@redhat.com>

From: Jérôme Glisse <jglisse@redhat.com>

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.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
---
 mm/hmm.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index b9f384ea15e9..74d69812d6be 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -170,16 +170,10 @@ 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);
 
-- 
2.17.2

