sheepdog: optimize reloading of inode

Current sheepdog driver reloads inode when in both cases of snapshot
and invalidateion with iSCSI multipath. In the first case, reloading
whole inode isn't required. This patch reduces the overhead produced
by whole reloading in the case of snapshot.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

usr/bs_sheepdog.c

@@ -642,22 +642,37 @@ static int read_object(struct sheepdog_access_info *ai, char *buf, uint64_t oid,
 		       int copies, unsigned int datalen, uint64_t offset,
 		       int *need_reload);
 
-static int reload_inode(struct sheepdog_access_info *ai)
+static int reload_inode(struct sheepdog_access_info *ai, int is_snapshot)
 {
 	int ret, need_reload = 0;
 	char tag[SD_MAX_VDI_TAG_LEN];
 	uint32_t vid;
 
-	memset(tag, 0, sizeof(tag));
+	if (is_snapshot) {
+		memset(tag, 0, sizeof(tag));
 
-	ret = find_vdi_name(ai, ai->inode.name, CURRENT_VDI_ID, tag, &vid, 0);
-	if (ret)
-		return -1;
+		ret = find_vdi_name(ai, ai->inode.name, CURRENT_VDI_ID, tag,
+				    &vid, 0);
+		if (ret)
+			return -1;
 
-	ret = read_object(ai, (char *)&ai->inode, vid_to_vdi_oid(vid),
-			  ai->inode.nr_copies, SD_INODE_SIZE, 0, &need_reload);
-	if (ret)
-		return -1;
+		ret = read_object(ai, (char *)&ai->inode, vid_to_vdi_oid(vid),
+				  ai->inode.nr_copies,
+				  offsetof(struct sheepdog_inode, data_vdi_id),
+				  0, &need_reload);
+		if (ret)
+			return -1;
+	} else {
+		ret = read_object(ai, (char *)&ai->inode,
+				  vid_to_vdi_oid(ai->inode.vdi_id),
+				  ai->inode.nr_copies, SD_INODE_SIZE, 0,
+				  &need_reload);
+		if (ret)
+			return -1;
+	}
+
+	ai->min_dirty_data_idx = UINT32_MAX;
+	ai->max_dirty_data_idx = 0;
 
 	return 0;
 }
@@ -709,6 +724,8 @@ static int read_write_object(struct sheepdog_access_info *ai, char *buf,
 		return 0;
 	case SD_RES_INODE_INVALIDATED:
 		dprintf("inode object is invalidated\n");
+		*need_reload = 2;
+		return 0;
 	case SD_RES_READONLY:
 		*need_reload = 1;
 		return 0;
@@ -784,7 +801,7 @@ static int update_inode(struct sheepdog_access_info *ai)
 	goto update;
 
 reload:
-	reload_inode(ai);
+	reload_inode(ai, 0);
 	need_reload_inode = 0;
 
 update:
@@ -853,7 +870,7 @@ static int sd_io(struct sheepdog_access_info *ai, int write, char *buf, int len,
 	pthread_rwlock_unlock(&ai->inode_lock); /* unlock current read lock */
 
 	pthread_rwlock_wrlock(&ai->inode_lock);
-	ret = reload_inode(ai);
+	ret = reload_inode(ai, 0);
 	if (ret) {
 		eprintf("failed to reload in read path\n");
 		goto out;
@@ -911,7 +928,13 @@ static int sd_io(struct sheepdog_access_info *ai, int write, char *buf, int len,
 					   old_oid, flags, &need_reload_inode);
 			if (!ret) {
 				if (need_reload_inode) {
-					ret = reload_inode(ai);
+					/* If need_reload_inode is 1,
+					 * snapshot was created.
+					 * If it is 2, inode object is
+					 * invalidated
+					 */
+					ret = reload_inode(ai,
+						   need_reload_inode == 1);
 					if (!ret)
 						goto retry;
 				}