[Devel] [PATCH rh7] ploop: Add comment about ploop_pvd_header::m_FirstBlockOffset

[Kirill Tkhai]

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/block/ploop/fmt_ploop1.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/block/ploop/fmt_ploop1.c b/drivers/block/ploop/fmt_ploop1.c
index 5ca9f257be31..f54b4bf2039c 100644
--- a/drivers/block/ploop/fmt_ploop1.c
+++ b/drivers/block/ploop/fmt_ploop1.c
@@ -659,6 +659,11 @@ static int expand_holes_bitmap(struct ploop_delta *delta,
 	if (!delta->holes_bitmap)
 		return 0;
 
+	/*
+	 * According to BUG_ON() in ploop1_prepare_grow(),
+	 * we do not support zero m_FirstBlockOffset
+	 * at least since 2013.
+	 */
 	md_off = vh->m_FirstBlockOffset >> log;
 	nr = md_off + vh->m_Size;