added CONFIG_CONCURRENT_DISK_OPS support back

node/handlers.c

@@ -904,17 +904,19 @@ static int init (void)
         }
     }
 
-#define GET_VAR_INT(var,name) \
+#define GET_VAR_INT(var,name,def)                   \
         s = getConfString(configFiles, 2, name); \
 	if (s){					\
 		var = atoi(s);\
 		free (s);\
-	}
-	GET_VAR_INT(nc_state.config_max_mem,      CONFIG_MAX_MEM);
-	GET_VAR_INT(nc_state.config_max_cores,    CONFIG_MAX_CORES);
-	GET_VAR_INT(nc_state.save_instance_files, CONFIG_SAVE_INSTANCES);
-    int disable_injection = 0;
-    GET_VAR_INT(disable_injection, CONFIG_DISABLE_KEY_INJECTION); 
+	} else { \
+        var = def; \
+    }
+	GET_VAR_INT(nc_state.config_max_mem,      CONFIG_MAX_MEM, 0);
+	GET_VAR_INT(nc_state.config_max_cores,    CONFIG_MAX_CORES, 0);
+	GET_VAR_INT(nc_state.save_instance_files, CONFIG_SAVE_INSTANCES, 0);
+    GET_VAR_INT(nc_state.concurrent_disk_ops, CONFIG_CONCURRENT_DISK_OPS, 1);
+    int disable_injection; GET_VAR_INT(disable_injection, CONFIG_DISABLE_KEY_INJECTION, 0); 
     nc_state.do_inject_key = !disable_injection;
     strcpy(nc_state.admin_user_id, EUCALYPTUS_ADMIN);
 
@@ -986,10 +988,10 @@ static int init (void)
         long long cache_bs_reserved_mb  = cache_meta.blocks_limit ? ((cache_meta.blocks_locked + cache_meta.blocks_unlocked) / 2048) : 0;
 
         // look up configuration file settings for work and cache size
-        long long conf_work_size_mb  = -1; GET_VAR_INT(conf_work_size_mb,  CONFIG_NC_WORK_SIZE);
-        long long conf_cache_size_mb = -1; GET_VAR_INT(conf_cache_size_mb, CONFIG_NC_CACHE_SIZE);
+        long long conf_work_size_mb; GET_VAR_INT(conf_work_size_mb,  CONFIG_NC_WORK_SIZE, -1);
+        long long conf_cache_size_mb; GET_VAR_INT(conf_cache_size_mb, CONFIG_NC_CACHE_SIZE, -1);
         { // accommodate legacy MAX_DISK setting by converting it
-            int max_disk_gb = -1; GET_VAR_INT(max_disk_gb, CONFIG_MAX_DISK);        
+            int max_disk_gb; GET_VAR_INT(max_disk_gb, CONFIG_MAX_DISK, -1);
             if (max_disk_gb != -1) {
                 if (conf_work_size_mb == -1) {
                     logprintfl (EUCAWARN, "warning: using deprecated setting %s for the new setting %s\n", CONFIG_MAX_DISK, CONFIG_NC_WORK_SIZE);
@@ -1121,9 +1123,9 @@ static int init (void)
 	// only load virtio config for kvm
 	if (!strncmp("kvm", hypervisor, CHAR_BUFFER_SIZE) ||
 		!strncmp("KVM", hypervisor, CHAR_BUFFER_SIZE)) {
-		GET_VAR_INT(nc_state.config_use_virtio_net, CONFIG_USE_VIRTIO_NET);
-		GET_VAR_INT(nc_state.config_use_virtio_disk, CONFIG_USE_VIRTIO_DISK);
-		GET_VAR_INT(nc_state.config_use_virtio_root, CONFIG_USE_VIRTIO_ROOT);
+		GET_VAR_INT(nc_state.config_use_virtio_net, CONFIG_USE_VIRTIO_NET, 0);
+		GET_VAR_INT(nc_state.config_use_virtio_disk, CONFIG_USE_VIRTIO_DISK, 0);
+		GET_VAR_INT(nc_state.config_use_virtio_root, CONFIG_USE_VIRTIO_ROOT, 0);
 	}
 	free (hypervisor);
 
@@ -1147,6 +1149,7 @@ static int init (void)
 	logprintfl(EUCAINFO, "physical memory available for instances: %lldMB\n", nc_state.mem_max);
 	logprintfl(EUCAINFO, "virtual cpu cores available for instances: %lld\n", nc_state.cores_max);
 
+
 	// adopt running instances
 	adopt_instances();
 

node/handlers.h

@@ -87,6 +87,7 @@ struct nc_state_t {
 	virConnectPtr conn;
 	boolean convert_to_disk;
         boolean do_inject_key;
+        int concurrent_disk_ops;
 	// defined max
 	long long config_max_mem;
 	long long config_max_cores;

storage/backing.c

@@ -84,6 +84,7 @@
 #include "backing.h"
 #include "iscsi.h"
 #include "vbr.h"
+#include "ipc.h" // sem
 
 #define CACHE_TIMEOUT_USEC  1000000LL*60*60*2 
 #define STORE_TIMEOUT_USEC  1000000LL*60*2
@@ -93,6 +94,8 @@
 static char instances_path [MAX_PATH];
 static blobstore * cache_bs = NULL;
 static blobstore * work_bs;
+static sem * disk_sem = NULL;
+
 extern struct nc_state_t nc_state;
 
 static void bs_errors (const char * msg) { 
@@ -172,6 +175,13 @@ int init_backing_store (const char * conf_instances_path, unsigned int conf_work
         return ERROR;
     }
 
+    // set the initial value of the semaphore to the number of 
+    // disk-intensive operations that can run in parallel on this node
+    if (nc_state.concurrent_disk_ops && (disk_sem = sem_alloc (nc_state.concurrent_disk_ops, "mutex")) == NULL) {
+        logprintfl (EUCAERROR, "failed to create and initialize disk semaphore\n");
+        return ERROR;
+    }
+
     return OK;
 }
 
@@ -347,12 +357,21 @@ int create_instance_backing (ncInstance * instance)
                                           TRUE, // make working copy of runtime-modifiable files
                                           (instance->do_inject_key)?(instance->keyName):(NULL), // the SSH key
                                           instance->instanceId); // ID is for logging
-    if (sentinel == NULL ||
-        art_implement_tree (sentinel, work_bs, cache_bs, work_prefix, INSTANCE_PREP_TIMEOUT_USEC) != OK) { // download/create/combine the dependencies
+    if (sentinel == NULL) {
         logprintfl (EUCAERROR, "[%s] error: failed to prepare backing for instance\n", instance->instanceId);
         goto out;
     }
-
+
+    sem_p (disk_sem);
+    // download/create/combine the dependencies
+    int rc = art_implement_tree (sentinel, work_bs, cache_bs, work_prefix, INSTANCE_PREP_TIMEOUT_USEC);
+    sem_v (disk_sem);
+
+    if (rc != OK) {
+        logprintfl (EUCAERROR, "[%s] error: failed to implement backing for instance\n", instance->instanceId);
+        goto out;
+    }
+
     if (save_instance_struct (instance)) // update instance checkpoint now that the struct got updated
         goto out;