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-rw-r--r--mm/migrate.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 6ae8a66a704..94875b26592 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -639,6 +639,23 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (!trylock_page(page)) {
if (!force)
goto move_newpage;
+
+ /*
+ * It's not safe for direct compaction to call lock_page.
+ * For example, during page readahead pages are added locked
+ * to the LRU. Later, when the IO completes the pages are
+ * marked uptodate and unlocked. However, the queueing
+ * could be merging multiple pages for one bio (e.g.
+ * mpage_readpages). If an allocation happens for the
+ * second or third page, the process can end up locking
+ * the same page twice and deadlocking. Rather than
+ * trying to be clever about what pages can be locked,
+ * avoid the use of lock_page for direct compaction
+ * altogether.
+ */
+ if (current->flags & PF_MEMALLOC)
+ goto move_newpage;
+
lock_page(page);
}