reimplement commit locking

4 files changed, 37 insertions, 0 deletions

diff --git a/src/commit/commit-algorithm.cpp b/src/commit/commit-algorithm.cpp
index a5d3415..46cfa58 100644
--- a/src/commit/commit-algorithm.cpp
+++ b/src/commit/commit-algorithm.cpp
@@ -1157,6 +1157,18 @@ commit::isCommitPathEffective(Cstore& cs, const Cpath& pcomps,
 bool
 commit::doCommit(Cstore& cs, CfgNode& cfg1, CfgNode& cfg2)
 {
+  /* get the lock first.
+   * note: the getCommitLock() interface provided by Cstore guarantees
+   * that the lock will be released upon process termination (either
+   * normally or abnormally), so this is all that is required in terms
+   * of commit locking.
+   */
+  if (!cs.getCommitLock()) {
+    OUTPUT_USER("Configuration system temporarily locked "
+                "due to another commit in progress\n");
+    return false;
+  }
+
   Cpath p;
   CfgNode *root = getCommitTree(&cfg1, &cfg2, p);
   if (!root) {
diff --git a/src/cstore/cstore.hpp b/src/cstore/cstore.hpp
index af4a56d..d6f6d67 100644
--- a/src/cstore/cstore.hpp
+++ b/src/cstore/cstore.hpp
@@ -177,6 +177,11 @@ public:
   bool markCfgPathCommitted(const Cpath& path_comps, bool is_delete);
   virtual bool clearCommittedMarkers() = 0;
   virtual bool commitConfig(commit::PrioNode& pnode) = 0;
+  virtual bool getCommitLock() = 0;
+    /* note: the getCommitLock() function must guarantee lock release/cleanup
+     * upon process termination (either normally or abnormally). there is no
+     * separate call for releasing the lock.
+     */
   // load
   bool loadFile(const char *filename);
 
diff --git a/src/cstore/unionfs/cstore-unionfs.cpp b/src/cstore/unionfs/cstore-unionfs.cpp
index 6ccdbf2..41ce008 100644
--- a/src/cstore/unionfs/cstore-unionfs.cpp
+++ b/src/cstore/unionfs/cstore-unionfs.cpp
@@ -63,6 +63,7 @@ const string UnionfsCstore::C_COMMENT_FILE = ".comment";
 const string UnionfsCstore::C_TAG_NAME = "node.tag";
 const string UnionfsCstore::C_VAL_NAME = "node.val";
 const string UnionfsCstore::C_DEF_NAME = "node.def";
+const string UnionfsCstore::C_COMMIT_LOCK_FILE = "/opt/vyatta/config/.lock";
 
 
 ////// static
@@ -696,6 +697,23 @@ UnionfsCstore::commitConfig(commit::PrioNode& node)
   return true;
 }
 
+bool
+UnionfsCstore::getCommitLock()
+{
+  int fd = creat(C_COMMIT_LOCK_FILE.c_str(), 0777);
+  if (fd < 0) {
+    // should not happen since all commit processes should have write access
+    output_internal("getCommitLock() failed to open lock file\n");
+    return false;
+  }
+  if (lockf(fd, F_TLOCK, 0) < 0) {
+    // locked by someone else
+    return false;
+  }
+  // got the lock
+  return true;
+}
+
 
 ////// virtual functions defined in base class
 /* check if current tmpl_path is a valid tmpl dir.
diff --git a/src/cstore/unionfs/cstore-unionfs.hpp b/src/cstore/unionfs/cstore-unionfs.hpp
index c7cd2d9..1240488 100644
--- a/src/cstore/unionfs/cstore-unionfs.hpp
+++ b/src/cstore/unionfs/cstore-unionfs.hpp
@@ -57,6 +57,7 @@ public:
   bool inSession();
   bool clearCommittedMarkers();
   bool commitConfig(commit::PrioNode& pnode);
+  bool getCommitLock();
 
 private:
   // constants
@@ -82,6 +83,7 @@ private:
   static const string C_TAG_NAME;
   static const string C_VAL_NAME;
   static const string C_DEF_NAME;
+  static const string C_COMMIT_LOCK_FILE;
 
   /* max size for a file.
    * currently this includes value file and comment file.