[PATCH] mm/dmapool.c: add lock protect in dma_pool_destroy

[qiang.zhang]

From: Zhang Qiang <qiang.zh...@windriver.com>

When traversing "pool->page" linked list, to prevent possible
other path operations this list, causing it to be destroyed, we
should add lock protect for this list in dma_pool_destroy func.

Signed-off-by: Zhang Qiang <qiang.zh...@windriver.com>
---
 mm/dmapool.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/dmapool.c b/mm/dmapool.c
index f9fb9bbd733e..f7375b25af6c 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -267,6 +267,9 @@ static void pool_free_page(struct dma_pool *pool, struct 
dma_page *page)
 void dma_pool_destroy(struct dma_pool *pool)
 {
        bool empty = false;
+       LIST_HEAD(discard);
+       struct dma_page *page,*h;
+       unsigned long flags;
 
        if (unlikely(!pool))
                return;
@@ -281,8 +284,8 @@ void dma_pool_destroy(struct dma_pool *pool)
                device_remove_file(pool->dev, &dev_attr_pools);
        mutex_unlock(&pools_reg_lock);
 
+       spin_lock_irqsave(&pool->lock, flags);
        while (!list_empty(&pool->page_list)) {
-               struct dma_page *page;
                page = list_entry(pool->page_list.next,
                                  struct dma_page, page_list);
                if (is_page_busy(page)) {
@@ -297,8 +300,12 @@ void dma_pool_destroy(struct dma_pool *pool)
                        list_del(&page->page_list);
                        kfree(page);
                } else
-                       pool_free_page(pool, page);
+                       list_move(&page->page_list, &discard);
        }
+       spin_unlock_irqrestore(&pool->lock, flags);
+
+       list_for_each_entry_safe(page, h, &discard, page_list)
+               pool_free_page(pool, page);
 
        kfree(pool);
 }
-- 
2.26.2