mm/cma: fix alloc_contig_range ret code/potential leak

If the call __alloc_contig_migrate_range() in alloc_contig_range returns
-EBUSY, processing continues so that test_pages_isolated() is called where
there is a tracepoint to identify the busy pages.  However, it is possible
for busy pages to become available between the calls to these two
routines.  In this case, the range of pages may be allocated.
Unfortunately, the original return code (ret == -EBUSY) is still set and
returned to the caller.  Therefore, the caller believes the pages were not
allocated and they are leaked.

Update the return code with the value from test_pages_isolated().

Link: http://lkml.kernel.org/r/20171120193930.23428-2-mike.kravetz@oracle.com


Fixes: 8ef5849f ("mm/cma: always check which page caused allocation failure")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Git-commit: 4260137bb6e0e0fcf8ee881cac411e1c6a171c2f
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git


Change-Id: Ic88ceadfa54322791636149d41bb2854da5890d2
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>