From: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/block_dev.c |    5 +++++
 1 file changed, 5 insertions(+)

diff -puN fs/block_dev.c~nr_blockdev_pages-in_interrupt-warning fs/block_dev.c
--- a/fs/block_dev.c~nr_blockdev_pages-in_interrupt-warning
+++ a/fs/block_dev.c
@@ -23,6 +23,8 @@
 #include <linux/uio.h>
 #include <linux/namei.h>
 #include <linux/log2.h>
+#include <linux/hardirq.h>
+
 #include <asm/uaccess.h>
 #include "internal.h"
 
@@ -406,6 +408,9 @@ long nr_blockdev_pages(void)
 {
 	struct block_device *bdev;
 	long ret = 0;
+
+	WARN_ON(in_interrupt());
+
 	spin_lock(&bdev_lock);
 	list_for_each_entry(bdev, &all_bdevs, bd_list) {
 		ret += bdev->bd_inode->i_mapping->nrpages;
_