cluster: do not allow to repin recursive pins as something else.

i.e. a direct pin can be repinned as recursive, but a recursive
pin cannot be pinned as direct (this fails in IPFS too).

Additionally, save a couple of calls to the datastore by obtaining the
existing pin only once.

allocate.go

@@ -47,7 +47,7 @@ import (
 // into account if the given CID was previously in a "pin everywhere" mode,
 // and will consider such Pins as currently unallocated ones, providing
 // new allocations as available.
-func (c *Cluster) allocate(ctx context.Context, hash cid.Cid, rplMin, rplMax int, blacklist []peer.ID, prioritylist []peer.ID) ([]peer.ID, error) {
+func (c *Cluster) allocate(ctx context.Context, hash cid.Cid, currentPin *api.Pin, rplMin, rplMax int, blacklist []peer.ID, prioritylist []peer.ID) ([]peer.ID, error) {
 	ctx, span := trace.StartSpan(ctx, "cluster/allocate")
 	defer span.End()
 
@@ -61,8 +61,7 @@ func (c *Cluster) allocate(ctx context.Context, hash cid.Cid, rplMin, rplMax int
 
 	// Figure out who is holding the CID
 	var currentAllocs []peer.ID
-	currentPin, err := c.PinGet(ctx, hash)
-	if err == nil {
+	if currentPin != nil {
 		currentAllocs = currentPin.Allocations
 	}
 	metrics := c.monitor.LatestMetrics(ctx, c.informers[0].Name())

cluster.go

@@ -1308,8 +1308,8 @@ func checkPinType(pin *api.Pin) error {
 
 // setupPin ensures that the Pin object is fit for pinning. We check
 // and set the replication factors and ensure that the pinType matches the
-// metadata consistently.
-func (c *Cluster) setupPin(ctx context.Context, pin *api.Pin) error {
+// metadata consistently. Returns the existing Pin object for this Cid if it exists.
+func (c *Cluster) setupPin(ctx context.Context, pin, existing *api.Pin) error {
 	ctx, span := trace.StartSpan(ctx, "cluster/setupPin")
 	defer span.End()
 
@@ -1322,18 +1322,24 @@ func (c *Cluster) setupPin(ctx context.Context, pin *api.Pin) error {
 		return errors.New("pin.ExpireAt set before current time")
 	}
 
-	existing, err := c.PinGet(ctx, pin.Cid)
-	if err != nil && err != state.ErrNotFound {
-		return err
+	if existing == nil {
+		return nil
 	}
 
-	if existing != nil && existing.Type != pin.Type {
+	// If an pin CID is already pin, we do a couple more checks
+	if existing.Type != pin.Type {
 		msg := "cannot repin CID with different tracking method, "
 		msg += "clear state with pin rm to proceed. "
 		msg += "New: %s. Was: %s"
 		return fmt.Errorf(msg, pin.Type, existing.Type)
 	}
 
+	if existing.Mode == api.PinModeRecursive && pin.Mode != api.PinModeRecursive {
+		msg := "cannot repin a CID which is already pinned in "
+		msg += "recursive mode (new pin is pinned as %s). Unpin it first."
+		return fmt.Errorf(msg, pin.Mode)
+	}
+
 	return checkPinType(pin)
 }
 
@@ -1365,8 +1371,13 @@ func (c *Cluster) pin(
 		return pin, true, err
 	}
 
+	existing, err := c.PinGet(ctx, pin.Cid)
+	if err != nil && err != state.ErrNotFound {
+		return pin, false, err
+	}
+
 	// setup pin might produce some side-effects to our pin
-	err := c.setupPin(ctx, pin)
+	err = c.setupPin(ctx, pin, existing)
 	if err != nil {
 		return pin, false, err
 	}
@@ -1379,8 +1390,7 @@ func (c *Cluster) pin(
 	// pins to the consensus layer even if they are, this should trigger the
 	// pin tracker and allows users to get re-pin operations by re-adding
 	// without having to use recover, which is naturally expected.
-	existing, err := c.PinGet(ctx, pin.Cid)
-	if err == nil &&
+	if existing != nil &&
 		pin.PinOptions.Equals(&existing.PinOptions) &&
 		len(blacklist) == 0 {
 		pin = existing
@@ -1396,6 +1406,7 @@ func (c *Cluster) pin(
 		allocs, err := c.allocate(
 			ctx,
 			pin.Cid,
+			existing,
 			pin.ReplicationFactorMin,
 			pin.ReplicationFactorMax,
 			blacklist,

rpc_api.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/ipfs/ipfs-cluster/api"
+	"github.com/ipfs/ipfs-cluster/state"
 	"github.com/ipfs/ipfs-cluster/version"
 
 	cid "github.com/ipfs/go-cid"
@@ -342,7 +343,12 @@ func (rpcapi *ClusterRPCAPI) BlockAllocate(ctx context.Context, in *api.Pin, out
 		return errFollowerMode
 	}
 
-	err := rpcapi.c.setupPin(ctx, in)
+	existing, err := rpcapi.c.PinGet(ctx, in.Cid)
+	if err != nil && err != state.ErrNotFound {
+		return err
+	}
+
+	err = rpcapi.c.setupPin(ctx, in, existing)
 	if err != nil {
 		return err
 	}
@@ -364,6 +370,7 @@ func (rpcapi *ClusterRPCAPI) BlockAllocate(ctx context.Context, in *api.Pin, out
 	allocs, err := rpcapi.c.allocate(
 		ctx,
 		in.Cid,
+		existing,
 		in.ReplicationFactorMin,
 		in.ReplicationFactorMax,
 		[]peer.ID{},        // blacklist