XFS: Free buffer pages array unconditionally

The code in xfs_free_buf() only attempts to free the b_pages array if the
buffer is a page cache backed or page allocated buffer. The extra log buffer
that is used when the log wraps uses pages that are allocated to a different
log buffer, but it still has a b_pages array allocated when those pages
are associated to with the extra buffer in xfs_buf_associate_memory.

Hence we need to always attempt to free the b_pages array when tearing
down a buffer, not just on buffers that are explicitly marked as page bearing
buffers. This fixes a leak detected by the kernel memory leak code.
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/linux-2.6/xfs_buf.c

@@ -292,6 +292,7 @@ _xfs_buf_free_pages(
 {
 	if (bp->b_pages != bp->b_page_array) {
 		kmem_free(bp->b_pages);
+		bp->b_pages = NULL;
 	}
 }
 
@@ -323,9 +324,8 @@ xfs_buf_free(
 				ASSERT(!PagePrivate(page));
 			page_cache_release(page);
 		}
-		_xfs_buf_free_pages(bp);
 	}
-
+	_xfs_buf_free_pages(bp);
 	xfs_buf_deallocate(bp);
 }