mm/gup: don't pin migrated cma pages in movable zone

Patch series "prohibit pinning pages in ZONE_MOVABLE", v11.

When page is pinned it cannot be moved and its physical address stays
the same until pages is unpinned.

This is useful functionality to allows userland to implementation DMA
access. For example, it is used by vfio in vfio_pin_pages().

However, this functionality breaks memory hotplug/hotremove assumptions
that pages in ZONE_MOVABLE can always be migrated.

This patch series fixes this issue by forcing new allocations during
page pinning to omit ZONE_MOVABLE, and also to migrate any existing
pages from ZONE_MOVABLE during pinning.

It uses the same scheme logic that is currently used by CMA, and extends
the functionality for all allocations.

For more information read the discussion [1] about this problem.
[1] https://lore.kernel.org/lkml/CA+CK2bBffHBxjmb9jmSKacm0fJMinyt3Nhk8Nx6iudcQSj80_w@mail.gmail.com

This patch (of 14):

In order not to fragment CMA the pinned pages are migrated.  However, they
are migrated to ZONE_MOVABLE, which also should not have pinned pages.

Remove __GFP_MOVABLE, so pages can be migrated to zones where pinning is
allowed.

Link: https://lkml.kernel.org/r/20210215161349.246722-1-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20210215161349.246722-2-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 71e546e279fcac5e3a9fd9d81d914d5d07f8d39b..b63e2c0df3c758500f68cc391b462432828cf618 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1616,7 +1616,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
        long ret = nr_pages;
        struct migration_target_control mtc = {
                .nid = NUMA_NO_NODE,
-               .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_NOWARN,
+               .gfp_mask = GFP_USER | __GFP_NOWARN,
        };
 
 check_again: