[SG] Add debug check for page alignment

Suggested by Boaz Harrosh <bharrosh@panasas.com>

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

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 42daf5e1526..df7ddcee7c4 100644
--- 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