[Sheepdog] [PATCH v6 7/8] collie: read the cached objects if any for collie operation

[Liu Yuan]

From: Liu Yuan <tailai.ly at taobao.com>

Collie operation such 'vdi list' or 'vdi object' need to read the lateset
VDI object, it might be cached in the object cache. We can't pass
SD_FLAG_CMD_CACHE to sheep because collie doesn't know if the cache mode is
enbled.

So we rely on the assumption that the cached object is freshest.

Signed-off-by: Liu Yuan <tailai.ly at taobao.com>
---
 sheep/store.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/sheep/store.c b/sheep/store.c
index c192aeb..4d84350 100644
--- a/sheep/store.c
+++ b/sheep/store.c
@@ -784,6 +784,14 @@ static int bypass_object_cache(struct sd_obj_req *hdr)
 {
 	uint64_t oid = hdr->oid;
 
+	/*
+	 * We assume the cached object is freshest, donot break it ever.
+	 * This assumption is useful for non-cache requests from collie,
+	 * which tries hard to get the newest data.
+	 */
+	if (object_is_cached(oid))
+		return 0;
+
 	if (!(hdr->flags & SD_FLAG_CMD_CACHE))
 		return 1;
 
-- 
1.7.8.2