remotes/ctr: allow to limit max concurrent uploads like downloads

Also add flags for push/pull subcommand to limit max concurrent
uploads/downloads.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

client.go

@@ -63,6 +63,7 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
+	"golang.org/x/sync/semaphore"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/backoff"
 	"google.golang.org/grpc/health/grpc_health_v1"
@@ -355,6 +356,9 @@ type RemoteContext struct {
 	// MaxConcurrentDownloads is the max concurrent content downloads for each pull.
 	MaxConcurrentDownloads int
 
+	// MaxConcurrentUploadedLayers is the max concurrent uploaded layers for each push.
+	MaxConcurrentUploadedLayers int
+
 	// AllMetadata downloads all manifests and known-configuration files
 	AllMetadata bool
 
@@ -463,7 +467,12 @@ func (c *Client) Push(ctx context.Context, ref string, desc ocispec.Descriptor,
 		wrapper = pushCtx.HandlerWrapper
 	}
 
-	return remotes.PushContent(ctx, pusher, desc, c.ContentStore(), pushCtx.PlatformMatcher, wrapper)
+	var limiter *semaphore.Weighted
+	if pushCtx.MaxConcurrentUploadedLayers > 0 {
+		limiter = semaphore.NewWeighted(int64(pushCtx.MaxConcurrentUploadedLayers))
+	}
+
+	return remotes.PushContent(ctx, pusher, desc, c.ContentStore(), limiter, pushCtx.PlatformMatcher, wrapper)
 }
 
 // GetImage returns an existing image