[PATCH 4/6] sheepdog: handle a case of snapshot -> failover

[Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>]

If refreshed inode is snapshot, we can reload entire inode and switch
to working VDI immediately.

Cc: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
Cc: Takashi Menjo <menjo.takashi@lab.ntt.co.jp>
Tested-by: Takashi Menjo <menjo.takashi@lab.ntt.co.jp>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
---
 usr/bs_sheepdog.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/usr/bs_sheepdog.c b/usr/bs_sheepdog.c
index ecb5033..8f228b5 100644
--- a/usr/bs_sheepdog.c
+++ b/usr/bs_sheepdog.c
@@ -704,6 +704,34 @@ static int reload_inode(struct sheepdog_access_info *ai, int is_snapshot)
 			ret = -1;
 			goto ret;
 		}
+
+		if (!!ai->inode.snap_ctime) {
+			/*
+			 * This is a case like below:
+			 * take snapshot -> write something -> failover
+			 *
+			 * Because invalidated inode is readonly and latest
+			 * working VDI can have COWed objects, we need to
+			 * resolve VID and reload its entire inode object.
+			 */
+			memset(tag, 0, sizeof(tag));
+
+			ret = find_vdi_name(ai, ai->inode.name, CURRENT_VDI_ID,
+					    tag, &vid, 0);
+			if (ret) {
+				ret = -1;
+				goto ret;
+			}
+
+			ret = read_object(ai, (char *)&ai->inode,
+					  vid_to_vdi_oid(vid),
+					  ai->inode.nr_copies, SD_INODE_SIZE, 0,
+					  &need_reload);
+			if (ret) {
+				ret = -1;
+				goto ret;
+			}
+		}
 	}
 
 	ai->min_dirty_data_idx = UINT32_MAX;
-- 
2.7.4