hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization

[linux-2.6-microblaze.git] / mm / migrate.c

diff --git a/mm/migrate.c b/mm/migrate.c
index 4389696..5d1839a 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1324,8 +1324,19 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
                goto put_anon;
 
        if (page_mapped(hpage)) {
+               struct address_space *mapping = page_mapping(hpage);
+
+               /*
+                * try_to_unmap could potentially call huge_pmd_unshare.
+                * Because of this, take semaphore in write mode here and
+                * set TTU_RMAP_LOCKED to let lower levels know we have
+                * taken the lock.
+                */
+               i_mmap_lock_write(mapping);
                try_to_unmap(hpage,
-                       TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
+                       TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS|
+                       TTU_RMAP_LOCKED);
+               i_mmap_unlock_write(mapping);
                page_was_mapped = 1;
        }