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

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/block_dev.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletion(-)

diff -puN fs/block_dev.c~mm-optimize-kill_bdev-fix fs/block_dev.c
--- a/fs/block_dev.c~mm-optimize-kill_bdev-fix
+++ a/fs/block_dev.c
@@ -55,9 +55,11 @@ static sector_t max_block(struct block_d
 	return retval;
 }
 
-/* Kill _all_ buffers, dirty or not.. */
+/* Kill _all_ buffers and pagecache , dirty or not.. */
 static void kill_bdev(struct block_device *bdev)
 {
+	if (bdev->bd_inode->i_mapping->nrpages == 0)
+		return;
 	invalidate_bh_lrus();
 	truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
 }	
_