[PATCHv2] CMA/HOTPLUG: clear buffer-head lru before page migration

[Gioh Kim]

The previous PATCH inserts invalidate_bh_lrus() only into CMA code.
HOTPLUG needs also dropping bh of lru.
So v2 inserts invalidate_bh_lrus() into both of CMA and HOTPLUG.


---------------------------- 8< ----------------------------
The bh must be free to migrate a page at which bh is mapped.
The reference count of bh is increased when it is installed
into lru so that the bh of lru must be freed before migrating the page.

This frees every bh of lru. We could free only bh of migrating page.
But searching lru sometimes costs more than invalidating entire lru.

Signed-off-by: Gioh Kim <gioh.kim@xxxxxxx>
Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
---
 mm/memory_hotplug.c |    1 +
 mm/page_alloc.c     |    2 ++
 2 files changed, 3 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a3797d3..1c5454f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1672,6 +1672,7 @@ repeat:
                lru_add_drain_all();
                cond_resched();
                drain_all_pages();
+               invalidate_bh_lrus();
        }

        pfn = scan_movable_pages(start_pfn, end_pfn);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b99643d4..c00dedf 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6369,6 +6369,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
        if (ret)
                return ret;

+       invalidate_bh_lrus();
+
        ret = __alloc_contig_migrate_range(&cc, start, end);
        if (ret)
                goto done;
--
1.7.9.5
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