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