4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mike Kravetz <[email protected]> commit 63cd448908b5eb51d84c52f02b31b9b4ccd1cb5a upstream. 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 comment to indicate that allocation is still possible even if __alloc_contig_migrate_range returns -EBUSY. Also, clear return code in this case so that it is not accidentally used or returned to caller. Link: http://lkml.kernel.org/r/[email protected] Fixes: 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure") Signed-off-by: Mike Kravetz <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Acked-by: Michal Hocko <[email protected]> Acked-by: Johannes Weiner <[email protected]> Acked-by: Joonsoo Kim <[email protected]> Cc: Michal Nazarewicz <[email protected]> Cc: Laura Abbott <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mel Gorman <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7587,11 +7587,18 @@ int alloc_contig_range(unsigned long sta /* * In case of -EBUSY, we'd like to know which page causes problem. - * So, just fall through. We will check it in test_pages_isolated(). + * So, just fall through. test_pages_isolated() has a tracepoint + * which will report the busy page. + * + * It is possible that busy pages could become available before + * the call to test_pages_isolated, and the range will actually be + * allocated. So, if we fall through be sure to clear ret so that + * -EBUSY is not accidentally used or returned to caller. */ ret = __alloc_contig_migrate_range(&cc, start, end); if (ret && ret != -EBUSY) goto done; + ret =0; /* * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
