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

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Message-Id: <20190129165428.3931-3-jglisse@redhat.com>
Date:   Tue, 29 Jan 2019 11:54:20 -0500
From:   jglisse@...hat.com
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH 02/10] mm/hmm: do not erase snapshot when a range is invalidated

From: Jérôme Glisse <jglisse@...hat.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@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: John Hubbard <jhubbard@...dia.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