feat(fsrepo): protect with a repo lockfile

NB: daemon is one spot the repo lock is typically acquired

cmd/ipfs/daemon.go

@@ -12,7 +12,7 @@ import (
 	cmdsHttp "github.com/jbenet/go-ipfs/commands/http"
 	core "github.com/jbenet/go-ipfs/core"
 	commands "github.com/jbenet/go-ipfs/core/commands"
-	daemon "github.com/jbenet/go-ipfs/core/daemon"
+	fsrepo "github.com/jbenet/go-ipfs/repo/fsrepo"
 	util "github.com/jbenet/go-ipfs/util"
 	"github.com/jbenet/go-ipfs/util/debugerror"
 )
@@ -89,13 +89,13 @@ func daemonFunc(req cmds.Request) (interface{}, error) {
 		return nil, err
 	}
 
-	// acquire the daemon lock _before_ constructing a node. we need to make
+	// acquire the repo lock _before_ constructing a node. we need to make
 	// sure we are permitted to access the resources (datastore, etc.)
-	lock, err := daemon.Lock(req.Context().ConfigRoot)
-	if err != nil {
+	repo := fsrepo.At(req.Context().ConfigRoot)
+	if err := repo.Open(); err != nil {
 		return nil, debugerror.Errorf("Couldn't obtain lock. Is another daemon already running?")
 	}
-	defer lock.Close()
+	defer repo.Close()
 
 	// OK!!! Now we're ready to construct the node.
 	// make sure we construct an online node.

cmd/ipfs/main.go

@@ -20,7 +20,6 @@ import (
 	cmdsCli "github.com/jbenet/go-ipfs/commands/cli"
 	cmdsHttp "github.com/jbenet/go-ipfs/commands/http"
 	core "github.com/jbenet/go-ipfs/core"
-	daemon "github.com/jbenet/go-ipfs/core/daemon"
 	repo "github.com/jbenet/go-ipfs/repo"
 	config "github.com/jbenet/go-ipfs/repo/config"
 	fsrepo "github.com/jbenet/go-ipfs/repo/fsrepo"
@@ -392,7 +391,7 @@ func commandShouldRunOnDaemon(details cmdDetails, req cmds.Request, root *cmds.C
 
 	// at this point need to know whether daemon is running. we defer
 	// to this point so that some commands dont open files unnecessarily.
-	daemonLocked := daemon.Locked(req.Context().ConfigRoot)
+	daemonLocked := fsrepo.LockedByOtherProcess(req.Context().ConfigRoot)
 
 	if daemonLocked {
 

repo/fsrepo/fsrepo.go

@@ -10,6 +10,7 @@ import (
 	repo "github.com/jbenet/go-ipfs/repo"
 	common "github.com/jbenet/go-ipfs/repo/common"
 	config "github.com/jbenet/go-ipfs/repo/config"
+	lockfile "github.com/jbenet/go-ipfs/repo/fsrepo/lock"
 	opener "github.com/jbenet/go-ipfs/repo/fsrepo/opener"
 	util "github.com/jbenet/go-ipfs/util"
 	debugerror "github.com/jbenet/go-ipfs/util/debugerror"
@@ -24,10 +25,13 @@ var (
 	// If an operation is used when repo is Open and the operation does not
 	// change the repo's state, the package lock does not need to be acquired.
 	openerCounter *opener.Counter
+
+	lockfiles map[string]io.Closer
 )
 
 func init() {
 	openerCounter = opener.NewCounter()
+	lockfiles = make(map[string]io.Closer)
 }
 
 // FSRepo represents an IPFS FileSystem Repo. It is not thread-safe.
@@ -74,6 +78,15 @@ func Remove(path string) error {
 	return os.RemoveAll(path)
 }
 
+// LockedByOtherProcess returns true if the FSRepo is locked by another
+// process. If true, then the repo cannot be opened by this process.
+func LockedByOtherProcess(repoPath string) bool {
+	openerCounter.Lock()
+	defer openerCounter.Unlock()
+	// NB: the lock is only held when repos are Open
+	return lockfile.Locked(repoPath) && openerCounter.NumOpeners(repoPath) == 0
+}
+
 // Open returns an error if the repo is not initialized.
 func (r *FSRepo) Open() error {
 	openerCounter.Lock()
@@ -118,9 +131,7 @@ func (r *FSRepo) Open() error {
 		return debugerror.Errorf("logs: %s", err)
 	}
 
-	r.state = opened
-	openerCounter.AddOpener(r.path)
-	return nil
+	return transitionToOpened(r)
 }
 
 // Config returns the FSRepo's config. This method must not be called if the
@@ -217,8 +228,7 @@ func (r *FSRepo) Close() error {
 	if r.state != opened {
 		return debugerror.Errorf("repo is %s", r.state)
 	}
-	openerCounter.RemoveOpener(r.path)
-	return nil // TODO release repo lock
+	return transitionToClosed(r)
 }
 
 var _ io.Closer = &FSRepo{}
@@ -258,3 +268,36 @@ func initCheckDir(path string) error {
 	}
 	return nil
 }
+
+// transitionToOpened manages the state transition to |opened|. Caller must hold
+// openerCounter lock.
+func transitionToOpened(r *FSRepo) error {
+	r.state = opened
+	if countBefore := openerCounter.NumOpeners(r.path); countBefore == 0 { // #first
+		closer, err := lockfile.Lock(r.path)
+		if err != nil {
+			return err
+		}
+		lockfiles[r.path] = closer
+	}
+	return openerCounter.AddOpener(r.path)
+}
+
+// transitionToClosed manages the state transition to |closed|. Caller must
+// hold openerCounter lock.
+func transitionToClosed(r *FSRepo) error {
+	r.state = closed
+	if err := openerCounter.RemoveOpener(r.path); err != nil {
+		return err
+	}
+	if countAfter := openerCounter.NumOpeners(r.path); countAfter == 0 {
+		closer, ok := lockfiles[r.path]
+		if !ok {
+			return errors.New("package error: lockfile is not held")
+		}
+		if err := closer.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}

repo/fsrepo/lock/lock.go

@@ -1,4 +1,4 @@
-package daemon
+package lock
 
 import (
 	"io"
@@ -10,6 +10,7 @@ import (
 )
 
 // LockFile is the filename of the daemon lock, relative to config dir
+// TODO rename repo lock and hide name
 const LockFile = "daemon.lock"
 
 func Lock(confdir string) (io.Closer, error) {
@@ -23,7 +24,6 @@ func Locked(confdir string) bool {
 	}
 	if lk, err := Lock(confdir); err != nil {
 		return true
-
 	} else {
 		lk.Close()
 		return false

repo/fsrepo/opener/counter.go

@@ -38,15 +38,17 @@ func (l *Counter) NumOpeners(repoPath string) int {
 
 // AddOpener messages that an FSRepo holds a handle to the repo at this path.
 // This method is not thread-safe. The caller must have this object locked.
-func (l *Counter) AddOpener(repoPath string) {
+func (l *Counter) AddOpener(repoPath string) error {
 	l.repos[key(repoPath)]++
+	return nil
 }
 
 // RemoveOpener messgaes that an FSRepo no longer holds a handle to the repo at
 // this path. This method is not thread-safe. The caller must have this object
 // locked.
-func (l *Counter) RemoveOpener(repoPath string) {
+func (l *Counter) RemoveOpener(repoPath string) error {
 	l.repos[key(repoPath)]--
+	return nil
 }
 
 func key(repoPath string) string {