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Message-Id: <1432239792-5002-7-git-send-email-jglisse@redhat.com>
Date: Thu, 21 May 2015 16:23:02 -0400
From: jglisse@...hat.com
To: akpm@...ux-foundation.org
Cc: <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
<joro@...tes.org>, Mel Gorman <mgorman@...e.de>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Johannes Weiner <jweiner@...hat.com>,
Larry Woodman <lwoodman@...hat.com>,
Rik van Riel <riel@...hat.com>,
Dave Airlie <airlied@...hat.com>,
Brendan Conoboy <blc@...hat.com>,
Joe Donohue <jdonohue@...hat.com>,
Duncan Poole <dpoole@...dia.com>,
Sherry Cheung <SCheung@...dia.com>,
Subhash Gutti <sgutti@...dia.com>,
John Hubbard <jhubbard@...dia.com>,
Mark Hairgrove <mhairgrove@...dia.com>,
Lucien Dunning <ldunning@...dia.com>,
Cameron Buschardt <cabuschardt@...dia.com>,
Arvind Gopalakrishnan <arvindg@...dia.com>,
Haggai Eran <haggaie@...lanox.com>,
Shachar Raindel <raindel@...lanox.com>,
Liran Liss <liranl@...lanox.com>,
Roland Dreier <roland@...estorage.com>,
Ben Sander <ben.sander@....com>,
Greg Stoner <Greg.Stoner@....com>,
John Bridgman <John.Bridgman@....com>,
Michael Mantor <Michael.Mantor@....com>,
Paul Blinzer <Paul.Blinzer@....com>,
Laurent Morichetti <Laurent.Morichetti@....com>,
Alexander Deucher <Alexander.Deucher@....com>,
Oded Gabbay <Oded.Gabbay@....com>,
Jérôme Glisse <jglisse@...hat.com>
Subject: [PATCH 26/36] HMM: fork copy migrated memory into system memory for child process.
From: Jérôme Glisse <jglisse@...hat.com>
When forking if process being fork had any memory migrated to some
device memory, we need to make a system copy for the child process.
Latter patches can revisit this and use the same COW semantic for
device memory.
Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
---
mm/hmm.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index 1208f64..143c6ab 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -487,7 +487,37 @@ int hmm_mm_fork(struct mm_struct *src_mm,
unsigned long start,
unsigned long end)
{
- return -ENOMEM;
+ unsigned long npages = (end - start) >> PAGE_SHIFT;
+ struct hmm_event event;
+ dma_addr_t *dst;
+ struct hmm *hmm;
+ pte_t *new_pte;
+ int ret;
+
+ hmm = hmm_ref(src_mm->hmm);
+ if (!hmm)
+ return -EINVAL;
+
+
+ dst = kzalloc(npages * sizeof(*dst), GFP_KERNEL);
+ if (!dst) {
+ hmm_unref(hmm);
+ return -ENOMEM;
+ }
+ new_pte = kzalloc(npages * sizeof(*new_pte), GFP_KERNEL);
+ if (!new_pte) {
+ kfree(dst);
+ hmm_unref(hmm);
+ return -ENOMEM;
+ }
+
+ hmm_event_init(&event, hmm, start, end, HMM_FORK);
+ ret = hmm_migrate_back(hmm, &event, dst_mm, dst_vma, new_pte,
+ dst, start, end);
+ hmm_unref(hmm);
+ kfree(new_pte);
+ kfree(dst);
+ return ret;
}
EXPORT_SYMBOL(hmm_mm_fork);
@@ -662,6 +692,12 @@ static void hmm_mirror_update_pte(struct hmm_mirror *mirror,
}
if (hmm_pte_test_valid_dev(hmm_pte)) {
+ /*
+ * On fork device memory is duplicated so no need to write
+ * protect it.
+ */
+ if (event->etype == HMM_FORK)
+ return;
*hmm_pte &= event->pte_mask;
if (!hmm_pte_test_valid_dev(hmm_pte))
hmm_pt_iter_directory_unref(iter, mirror->pt.llevel);
--
1.9.3
--
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