mm: add a might_sleep_if in dma_pool_alloc

Buggy drivers (e.g. fsl_udc) could call dma_pool_alloc from atomic context with GFP_KERNEL. In most instances, the first pool_alloc_page call would succeed and the sleeping functions would never be called. This allowed the buggy drivers to slip through the cracks.

Add a might_sleep_if checking for __GFP_WAIT in flags.

---
 mm/dmapool.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

index 3df0637..4df2de7 100644
@@ -311,6 +311,8 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
 	size_t offset;
 	void *retval;
 
+	might_sleep_if(mem_flags & __GFP_WAIT);
+
 	spin_lock_irqsave(&pool->lock, flags);
  restart:
 	list_for_each_entry(page, &pool->page_list, page_list) {

1.6.6

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