linux-kernel - [PATCH 0/1] make start_isolate_page

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Date:   Mon, 26 Feb 2018 11:10:53 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH 0/1] make start_isolate_page_range() thread safe

This patch was included in the RFC series "Interface for higher order
contiguous allocations".
http://lkml.kernel.org/r/20180212222056.9735-1-mike.kravetz@oracle.com

Since there have been few comments on the RFC and this patch addresses
a real issue with the current code, I am sending it separately.

To verify this is a real issue, I created a large CMA area at boot time.
I wrote some code to exercise large allocations and frees via cma_alloc()
and cma_release().  At the same time, I had a script just allocate and
free gigantic pages via the sysfs interface.

After a little bit of running, 'free memory' on the system went to
zero.  After 'stopping' the tests, I observed that most zone normal
page blocks were marked as MIGRATE_ISOLATE.  Hence 'not available'.

I suspect there are few (if any) systems employing both CMA and
dynamic gigantic huge page allocation.  However, it is probably a
good idea to fix this issue.  Because this is so unlikely, I am not
sure if this should got to stable releases as well.

Mike Kravetz (1):
  mm: make start_isolate_page_range() fail if already isolated

 mm/page_alloc.c     |  8 ++++----
 mm/page_isolation.c | 10 +++++++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

-- 
2.13.6