[SG] Add debug check for page alignment

Suggested by Boaz Harrosh <bharrosh@panasas.com>

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 42daf5e..df7ddce 100644 (file)
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -41,6 +41,11 @@ static inline void sg_set_page(struct scatterlist *sg, struct page *page)
 {
        unsigned long page_link = sg->page_link & 0x3;
 
+       /*
+        * In order for the low bit stealing approach to work, pages
+        * must be aligned at a 32-bit boundary as a minimum.
+        */
+       BUG_ON((unsigned long) page & 0x03);
 #ifdef CONFIG_DEBUG_SG
        BUG_ON(sg->sg_magic != SG_MAGIC);
 #endif