linux-kernel - [PATCH] mm/hmm: Fix initial PFN for hugetlbfs pages

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Message-ID: <20190419223737.32111-1-rcampbell@nvidia.com>
Date:   Fri, 19 Apr 2019 15:37:37 -0700
From:   <rcampbell@...dia.com>
To:     <linux-mm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ira Weiny <ira.weiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] mm/hmm: Fix initial PFN for hugetlbfs pages

From: Ralph Campbell <rcampbell@...dia.com>

The mmotm patch [1] adds hugetlbfs support for HMM but the initial
PFN used to fill the HMM range->pfns[] array doesn't properly
compute the starting PFN offset.
This can be tested by running test-hugetlbfs-read from [2].

Fix the PFN offset by adjusting the page offset by the device's
page size.

Andrew, this should probably be squashed into Jerome's patch.

[1] https://marc.info/?l=linux-mm&m=155432003506068&w=2
("mm/hmm: mirror hugetlbfs (snapshoting, faulting and DMA mapping)")
[2] https://gitlab.freedesktop.org/glisse/svm-cl-tests

Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
Cc: Jérôme Glisse <jglisse@...hat.com>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Balbir Singh <bsingharora@...il.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Souptick Joarder <jrdr.linux@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 mm/hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index def451a56c3e..fcf8e4fb5770 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -868,7 +868,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 		goto unlock;
 	}
 
-	pfn = pte_pfn(entry) + (start & mask);
+	pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
 	for (; addr < end; addr += size, i++, pfn += pfn_inc)
 		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 				 cpu_flags;
-- 
2.20.1