[PATCH 0/1] make start_isolate_page_range() thread safe

[Mike Kravetz]

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

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(-)

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2.13.6